Affinsy Rankings · July 2026 edition

Best Retention & CRO Agencies in the UK, 2026

The 15 strongest retention, lifecycle and CRO agencies we found for e-commerce brands in the UK, scored 0-100 on proven results, specialization, data sophistication, reputation and track record. This is Affinsy's opinionated take, weighted toward demonstrated data work; rank position is never purchasable.

Evidence collected July 2026 · Updated July 15, 2026

01 · The ranking

Email / SMS lifecycleCRO / experimentationFull retention

Debut edition · rank movement appears from the next refresh

#183/ 100

Underground Ecom

Email / SMS

London, UK · Email/SMS lifecycle & retention · undergroundecom.com · Founded 2018

London-headquartered retention agency (~100 staff) that is Klaviyo's largest Elite partner globally. Named Klaviyo Agency Partner of the Year EMEA 2025.

Why this rank: Leads the UK list on nearly every pillar: quantified cases (SeoulBox +287% revenue), top Klaviyo tier, evidenced RFM/LTV/testing capability, benchmarks data product and real review volume. The reference point for the category in Europe.

Results

27/30

Specialization

20/20

Data sophistication

17/20

Reputation

11/15

Track record

8/15

How this score breaks down

Results27/30

Documented outcomes: SeoulBox +287% revenue; Klaviyo's largest Elite partner globally; Agency Partner of the Year EMEA 2025

Specialization20/20

Credentials: Klaviyo Elite Master

Data sophistication17/20

Evidenced: segmentation / RFM (+5), structured testing (+4), attribution (+3), predictive LTV (+5) · not evidenced: CDP Not yet verified

Reputation11/15

Reviews: 4.5/5 across 39 on Trustpilot, plus awards and community footprint

Track record8/15

Operating: since 2018 (8 years), team ~90-100

Klaviyo Elite Master·4.5/5 · 39 reviews (Trustpilot)Not yet verifiedVerify or update this listing →

#266/ 100

ConversionWise

CRO

Bristol, UK · CRO / conversion design for Shopify DTC · conversionwise.com · Founded 2013

Bristol conversion-design agency (70+ team) focused on post-click optimization for Shopify DTC: landing pages, offer testing and conversion-focused design for 4,000+ brands since 2013.

Why this rank: Unmatched scale and social proof in UK CRO (462 Trustpilot reviews at 4.9; GBP 1B+ tracked client revenue). Design-led methodology shows less deep experimentation/data evidence than research-driven CRO firms, which caps the data pillar.

Results

28/30

Specialization

10/20

Data sophistication

4/20

Reputation

10/15

Track record

14/15

How this score breaks down

Results28/30

Documented outcomes: 4,000+ DTC brands; GBP 1B+ tracked client revenue; 7,500+ conversion pages since 2013

Specialization10/20

Credentials: Conversion Rate Academy; 70+ team

Data sophistication4/20

Evidenced: structured testing (+4) · not evidenced: segmentation / RFM, predictive LTV, attribution, CDP Not yet verified

Reputation10/15

Reviews: 4.9/5 across 462 on Trustpilot, plus awards and community footprint

Track record14/15

Operating: since 2013 (13 years), team 70+

Conversion Rate Academy; 70+ team·4.9/5 · 462 reviews (Trustpilot)Not yet verifiedVerify or update this listing →

#365/ 100

AWA Digital

CRO

London, UK · E-commerce CRO / experimentation · awa-digital.com · Founded 2009

London e-commerce CRO specialist since 2009 with offices on three continents; co-authored the bestselling Kogan Page book 'E-commerce Website Optimization'.

Why this rank: Deep veteran track record and enterprise-grade cases (Canon Europe across 13 territories at 1,200% ROI; 2x CRO Agency of the Year). No visible review presence is the main deduction.

Results

27/30

Specialization

17/20

Data sophistication

7/20

Reputation

5/15

Track record

9/15

How this score breaks down

Results27/30

Documented outcomes: Canon Europe: CRO in 13 territories, 1,200% ROI; 2x CRO Agency of the Year; bestselling CRO book

Specialization17/20

Credentials: 2x CRO Agency of the Year

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation5/15

Reviews: none found publicly; scored on awards and community footprint

Track record9/15

Operating: since 2009 (17 years), team senior team

2x CRO Agency of the Year·No public reviews foundNot yet verifiedVerify or update this listing →

#465/ 100

PAASE

Email / SMS

Milton Keynes area, UK · AI/data-driven email & SMS retention · paase.co.uk · Founded 2019

Milton Keynes-area retention agency and the first Klaviyo Elite Master headquartered in EMEA, positioning around AI and predictive data-driven email/SMS.

Why this rank: Top-tier specialization and genuine predictive/LTV work (Okanui +233% automated revenue), but a thin public reputation footprint - few reviews, little community presence - keeps it behind Underground Ecom.

Results

27/30

Specialization

20/20

Data sophistication

10/20

Reputation

3/15

Track record

5/15

How this score breaks down

Results27/30

Documented outcomes: Okanui +233% automated revenue; first EMEA-based Klaviyo Elite Master

Specialization20/20

Credentials: Klaviyo Elite Master (first in EMEA)

Data sophistication10/20

Evidenced: segmentation / RFM (+5), predictive LTV (+5) · not evidenced: structured testing, attribution, CDP Not yet verified

Reputation3/15

Reviews: none found publicly; scored on awards and community footprint

Track record5/15

Operating: since 2019 (7 years), team unknown

Klaviyo Elite Master (first in EMEA)·No public reviews foundNot yet verifiedVerify or update this listing →

#563/ 100

Magnet Monster

Email / SMS

Manchester, UK · Email/SMS/WhatsApp retention boutique · magnetmonster.com · Founded 2018

Manchester email/SMS/WhatsApp retention boutique founded by Adam Kitchen; Klaviyo Master Platinum, ~150 DTC brands served, with founder-led courses and content.

Why this rank: Strong documented outcomes (client email to 30% of total revenue within 90 days) and a high Klaviyo tier. No third-party review presence at all - fixing that alone would lift it a band.

Results

27/30

Specialization

17/20

Data sophistication

9/20

Reputation

2/15

Track record

8/15

How this score breaks down

Results27/30

Documented outcomes: Stranded Hair Group: email to 30% of total revenue within 90 days; ~150 DTC brands served

Specialization17/20

Credentials: Klaviyo Master Platinum

Data sophistication9/20

Evidenced: segmentation / RFM (+5), structured testing (+4) · not evidenced: predictive LTV, attribution, CDP Not yet verified

Reputation2/15

Reviews: none found publicly; scored on awards and community footprint

Track record8/15

Operating: since 2018 (8 years), team boutique

Klaviyo Master Platinum·No public reviews foundNot yet verifiedVerify or update this listing →

#661/ 100

Blend Commerce

CRO

Stratford-upon-Avon, UK · Shopify CRO/CVO + Klaviyo retention · blendcommerce.com · Founded 2017

Stratford-upon-Avon agency combining Shopify CVO (customer value optimization) with Klaviyo retention; named Global CRO Agency of the Year 2026.

Why this rank: The most balanced UK profile - results, RFM/testing/attribution evidence and awards all solid. A plain Klaviyo partner tier (no Master level) is what separates it from the top three.

Results

26/30

Specialization

10/20

Data sophistication

12/20

Reputation

7/15

Track record

6/15

How this score breaks down

Results26/30

Documented outcomes: +61% subscription sign-ups, +14% store CVR; Global CRO Agency of the Year 2026

Specialization10/20

Credentials: Klaviyo partner; Global CRO Agency of the Year 2026

Data sophistication12/20

Evidenced: segmentation / RFM (+5), structured testing (+4), attribution (+3) · not evidenced: predictive LTV, CDP Not yet verified

Reputation7/15

Reviews: none found publicly; scored on awards and community footprint

Track record6/15

Operating: since 2017 (9 years), team in-house team

Klaviyo partner; Global CRO Agency of the Year 2026·No public reviews foundNot yet verifiedVerify or update this listing →

#759/ 100

Enchant Agency

Email / SMS

London, UK · Email/CRM lifecycle, Klaviyo migrations · enchantagency.com · Founded 2014

London email/CRM lifecycle agency founded 2014 by global email speaker Philip Storey; Klaviyo Platinum Master specializing in complex migrations and automation.

Why this rank: High tier, a Klaviyo Klicks award and a striking headline (client email revenue +1000% over three years), but a small volume of published, numbered case studies limits the results pillar.

Results

19/30

Specialization

17/20

Data sophistication

12/20

Reputation

4/15

Track record

7/15

How this score breaks down

Results19/30

Documented outcomes: Client email revenue +1000% over 3 years; Victorinox, Sealskinz; Klaviyo Klicks Award 2023

Specialization17/20

Credentials: Klaviyo Platinum Master

Data sophistication12/20

Evidenced: segmentation / RFM (+5), structured testing (+4), attribution (+3) · not evidenced: predictive LTV, CDP Not yet verified

Reputation4/15

Reviews: none found publicly; scored on awards and community footprint

Track record7/15

Operating: since 2014 (12 years), team boutique

Klaviyo Platinum Master·No public reviews foundNot yet verifiedVerify or update this listing →

#857/ 100

Melusine Studio

Email / SMS

London, UK · Email/SMS lifecycle for premium DTC · melusine.studio · Founded 2020

Remote-first London studio (~15 people) running email/SMS lifecycle for premium DTC brands in English and French markets; clients include REFY and Daniel Wellington.

Why this rank: Klaviyo Platinum Master with good quantified work (+45% client turnover in a year). Young, with no review or community footprint yet - reputation is the growth area.

Results

26/30

Specialization

17/20

Data sophistication

9/20

Reputation

0/15

Track record

5/15

How this score breaks down

Results26/30

Documented outcomes: Client turnover +45% in a year; clients incl. REFY, Daniel Wellington

Specialization17/20

Credentials: Klaviyo Platinum Master

Data sophistication9/20

Evidenced: segmentation / RFM (+5), structured testing (+4) · not evidenced: predictive LTV, attribution, CDP Not yet verified

Reputation0/15

Reviews: none found publicly; scored on awards and community footprint

Track record5/15

Operating: since 2020 (6 years), team ~15

Klaviyo Platinum Master·No public reviews foundNot yet verifiedVerify or update this listing →

#955/ 100

Endless Gain

CRO

Manchester, UK · CRO with biometrics & behavioural psychology · endlessgain.com · Founded 2016

Manchester CRO agency (~25 consultants) differentiating through biometrics, eye-tracking and behavioural psychology rather than standard A/B iteration.

Why this rank: Distinctive methodology and occasional huge discoveries (one experiment worth $7m/year globally). Fewer platform certifications and reviews than the firms above it.

Results

27/30

Specialization

10/20

Data sophistication

7/20

Reputation

3/15

Track record

8/15

How this score breaks down

Results27/30

Documented outcomes: Single experiment discovery worth $7m/annum globally; clients Dreams, Shark Ninja

Specialization10/20

Credentials: Biometrics-led CRO

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation3/15

Reviews: none found publicly; scored on awards and community footprint

Track record8/15

Operating: since 2016 (10 years), team ~25

Biometrics-led CRO·No public reviews foundNot yet verifiedVerify or update this listing →

#1052/ 100

Converted

CRO

Sheffield & London, UK · CRO / experimentation (D2C, subscription) · converted.co.uk · Founded

Sheffield/London CRO practice for D2C, e-commerce and subscription businesses, with 15+ years of experimentation experience.

Why this rank: Solid quantified results (+163% visitor-to-booking conversion), but an anonymous team page, no reviews and no certifications make it hard to verify depth - transparency would move it up.

Results

26/30

Specialization

10/20

Data sophistication

7/20

Reputation

0/15

Track record

9/15

How this score breaks down

Results26/30

Documented outcomes: +163% visitor-to-booking conversion for London Travel Clinic

Specialization10/20

Credentials: 15+ years CRO experience

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation0/15

Reviews: none found publicly; scored on awards and community footprint

Track record9/15

Operating: since (2026 years), team unknown

15+ years CRO experience·No public reviews foundNot yet verifiedVerify or update this listing →

#1147/ 100

OptiExperts

CRO

London, UK · Shopify-exclusive CRO (SiteLab membership) · optiexperts.co.uk · Founded 2018

London boutique working exclusively on CRO for Shopify and Shopify Plus stores via its 'SiteLab' structured experimentation membership; Shopify Plus partner since 2018.

Why this rank: One of the best independently verified uplifts in the UK list (+139% conversion in 3 months, Shoplift-verified). Small scale and only a couple of reviews cap reputation and track record.

Results

23/30

Specialization

10/20

Data sophistication

7/20

Reputation

2/15

Track record

5/15

How this score breaks down

Results23/30

Documented outcomes: +139% conversion in 3 months (2.22% to 5.31%), Shoplift-verified; works exclusively on Shopify/Plus CRO

Specialization10/20

Credentials: Shopify Plus partner since 2018

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation2/15

Reviews: 5/5 across 2 on Clutch, plus awards and community footprint

Track record5/15

Operating: since 2018 (8 years), team 10-20

Shopify Plus partner since 2018·5/5 · 2 reviews (Clutch)Not yet verifiedVerify or update this listing →

#1243/ 100

PM Digital

CRO

Northern Ireland (remote), UK · Shopify CRO for 7-9 figure DTC brands · pmdigitaldesign.com · Founded

Northern Ireland remote-first team (~16) doing Shopify CRO for 7-to-9-figure DTC brands, with an avatar/awareness-level parallel testing system and a public CRO learning hub.

Why this rank: Interesting methodology and real numbers (Ripley Rader GBP 1.5m+ revenue, +22% RPV), but credentials are self-stated and there's no third-party review presence yet.

Results

20/30

Specialization

6/20

Data sophistication

12/20

Reputation

2/15

Track record

3/15

How this score breaks down

Results20/30

Documented outcomes: Ripley Rader: GBP 1.5m+ revenue, +22% revenue per visitor; avatar-segmented parallel testing system

Specialization6/20

Credentials: Shopify Partner (self-stated); CRO Learning Hub

Data sophistication12/20

Evidenced: structured testing (+4), attribution (+3), segmentation / RFM (+5) · not evidenced: predictive LTV, CDP Not yet verified

Reputation2/15

Reviews: none found publicly; scored on awards and community footprint

Track record3/15

Operating: since (2026 years), team ~16

Shopify Partner (self-stated); CRO Learning Hub·No public reviews foundNot yet verifiedVerify or update this listing →

#1342/ 100

Browser to Buyer

CRO

London, UK · Full-service ecommerce CRO · browsertobuyer.com · Founded

London full-service e-commerce CRO agency led by Dave Gowans, formerly of Conversion.com; Convert.com certified partner.

Why this rank: Credible pedigree and strong claims (average +30% CVR in six months, minimum 10x ROI), but claims are aggregate and unverified - itemized case studies would substantially raise the results score.

Results

18/30

Specialization

14/20

Data sophistication

7/20

Reputation

1/15

Track record

2/15

How this score breaks down

Results18/30

Documented outcomes: Avg +30% CVR within 6 months, min 10x ROI claimed; +GBP 1m sales in year one for a client

Specialization14/20

Credentials: Convert.com certified partner

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation1/15

Reviews: none found publicly; scored on awards and community footprint

Track record2/15

Operating: since (2026 years), team founder-led

Convert.com certified partner·No public reviews foundNot yet verifiedVerify or update this listing →

#1437/ 100

Customers Who Click

CRO

London, UK · Performance-based CRO for ecommerce/DTC · customerswhoclick.com · Founded

London performance-based CRO shop for e-commerce/DTC founded by Will Laurenson, who hosts the Customers Who Click podcast; offers a $100k revenue guarantee model.

Why this rank: The guarantee model and content presence are distinctive, but there is minimal verifiable evidence: no reviews, no certifications, and case results shown without client names or context.

Results

18/30

Specialization

4/20

Data sophistication

7/20

Reputation

5/15

Track record

3/15

How this score breaks down

Results18/30

Documented outcomes: A/B test wins of +45% and +70%; $100k revenue guarantee model; CRO podcast + newsletter

Specialization4/20

Credentials: No certs found; performance-fee model

Data sophistication7/20

Evidenced: structured testing (+4), attribution (+3) · not evidenced: segmentation / RFM, predictive LTV, CDP Not yet verified

Reputation5/15

Reviews: none found publicly; scored on awards and community footprint

Track record3/15

Operating: since (2026 years), team <10

No certs found; performance-fee model·No public reviews foundNot yet verifiedVerify or update this listing →

#1524/ 100

Sendfluence

Email / SMS

UK (remote), UK · Email/SMS lifecycle, performance-fee model · sendfluence.co.uk · Founded

Small founder-led UK Klaviyo agency running email/SMS lifecycle on a performance-fee pricing model.

Why this rank: Certified Klaviyo partner, but no published case studies, near-zero review presence and unknown track record - the least public evidence in the UK list. Claiming and documenting results would change its position quickly.

Results

5/30

Specialization

10/20

Data sophistication

5/20

Reputation

2/15

Track record

2/15

How this score breaks down

Results5/30

Documented outcomes: Performance-based pricing model; certified Klaviyo experts

Specialization10/20

Credentials: Klaviyo Partner

Data sophistication5/20

Evidenced: segmentation / RFM (+5) · not evidenced: predictive LTV, structured testing, attribution, CDP Not yet verified

Reputation2/15

Reviews: 4.5/5 across 1 on Google, plus awards and community footprint

Track record2/15

Operating: since (2026 years), team small, founder-led

Klaviyo Partner·4.5/5 · 1 reviews (Google)Not yet verifiedVerify or update this listing →

United States ranking →DACH ranking →

02 · Methodology

How agencies are scored

Every agency is scored 0-100 across five pillars from publicly verifiable evidence collected in July 2026. Evidence is weighted by tier: independently verified beats self-published, self-published beats claimed. The weighting is ours and deliberately favors data-driven operators; we publish the full rubric so you can disagree with it.

The Data Sophistication pillar is scored from public claims until verified. Verification means showing the data work behind the listing: the fastest route is one free Affinsy analysis on a client store, but any credible evidence counts. Verified listings carry the ✓ Verified Data-Driven badge from the next monthly edition.

Proven results

Quantified case studies: email revenue share, LTV, CVR, repeat rate. Volume and standout bonuses on top of an evidence base score.

Specialization

Klaviyo partner tier (Elite > Master Platinum > Master Gold > Platinum > Partner) or CRO-platform credentials. Self-claimed expertise scores low.

Data sophistication

Segmentation / RFM, predictive LTV, structured testing program, attribution, CDP. Scored from each agency's public claims until verified with real evidence.

Reputation

Third-party review volume and rating, industry awards, community footprint.

Track record

Years operating and client volume in e-commerce retention or CRO.

Excluded during sourcing: platform and tool vendors (Ebbo, ELAINE, Salesfire), absorbed agencies (Electriq), experimentation firms without an e-commerce-primary practice (Conversion.com, Cro Metrics, Speero, Daydot, Creative CX), generalists (WAUMEDIA, e-dialog), and agencies whose claims could not be verified (REO).

03 · Verification

Earn the Verified Data-Driven badge

Show the data work behind your listing: run a free analysis on one client store, or submit equivalent evidence. The badge lands in the next monthly edition.

Verify or update your listing →

Verification is free · Rank position is never purchasable