Paid social agency for ecommerce: UK brand comparison checklist

What to take away

Judge a paid social agency for ecommerce on catalogue integrity, consent records and margin-based targets, not on how many creatives it promises each month.
Ask who owns the ad account, product catalogue, pixel and conversion data at the end of the contract, and get the answer in writing.
Treat every agency ad spend figure as unverified unless it names a source and a date.
Build one comparison table before the first call, so each agency answers identical questions.

Why ecommerce briefs differ from lead generation

Ecommerce paid social sells a catalogue, so one stale price or a sold-out variant can waste spend across thousands of impressions.

Lead generation briefs tolerate a slower feedback loop, because a form fill still holds value a week later. Retail does not work that way.

The first comparison question is operational: can the agency keep product feeds, stock levels and prices synchronised with the ad account every working day? Agencies built around B2B pipelines often cannot, and they rarely say so before the contract.

What to put in the comparison checklist

Confirm the legal entity, its company number and its registered trading address on the Companies House register before discussing scope.
Ask which ecommerce platforms the agency works with in practice, and how a catalogue update reaches the ad account.
Ask who owns the ad account, the pixel, the product catalogue and the conversion data when the contract ends.
Ask how the agency sets targets, and whether it uses your gross margin or the platform's reported return.
Ask how consent is captured for retargeting audiences, and which lawful basis the agency assumes.
Ask what happens to live campaigns when a product goes out of stock or a price changes.
Ask for a written exit route, including the data export format and a handover date.

Score every row before the second call, so two agencies can be read side by side. A usable answer names a person, a process and a date; a weak answer stays general.

What to check	A weak answer	A usable answer
Catalogue and feeds	"We connect Shopify to Meta."	Names the feed method, the update frequency and who fixes a failed sync.
Account and data ownership	"It all sits under our partner access."	Confirms your business holds super admin on the ad account and the catalogue, and names the export format.
Targets and reporting	"We optimise to return on ad spend."	Sets the target from your gross margin and reconciles platform totals against your own order data.
Consent for retargeting	"We are GDPR compliant."	Names the lawful basis, the consent record kept and who reviews the audience list.
Exit and handover	"We help with the transition."	Gives the notice period, the data export format and a handover date.

Weak vs usable agency answers

Weak answer

Catalogue updates: Creative only, feed left
Account ownership: Assets sit with agency
Target setting: Return figure, no calculation
Exit: Handled at contract end

Usable answer

Catalogue updates: Named feed schedule and owner
Account ownership: Client-owned account, partner access
Target setting: Margin-based target with inputs
Exit: Export format, date, handover contact

Platform fit: Shopify, Magento and the rest

Shopify suits smaller catalogues, because app-based feeds are quick to connect. Magento and Adobe Commerce suit larger catalogues with variants, currencies and trade pricing, but they need a feed process rather than a plugin.

Ask the agency to describe the last catalogue migration it ran, not the last campaign it launched. Meta's own ads documentation sets out the catalogue and shopping formats an agency should be able to configure.

Setting ad spend from margin, not from a benchmark

UK ecommerce ad spend is best set from unit economics. No public average tells you what your shop can afford, and an agency quoting one is quoting somebody else's business.

Illustrative arithmetic only: if gross margin is 40 per cent and average order value is £50, then £20 of each order is left before fixed costs. A monthly ad budget of £10,000 therefore needs about 500 orders to break even.

Ask the agency to repeat the sum with your postage, payment and returns costs included, and to show the working in writing.

Consent, claims and platform rules

Retargeting is where ecommerce paid social most often breaks the rules. The ICO's direct marketing guidance covers consent, soft opt-in and the records you must keep, and it applies across the UK.

Your own business carries a duty here too. Under the Data Protection (Charges and Information) Regulations 2018, organisations that use personal information must pay a data protection fee unless they are exempt, and the ICO's fee self-assessment shows which tier applies. The ICO's three fee tiers run from £52 to £3,763, so an agency handling your customer audiences should be able to confirm its own registration before you share a list.

Ad copy is covered too. The CAP Code, enforced by the ASA, applies across the UK, including Scotland, Wales and Northern Ireland. Discount claims, countdown timers and previous-price comparisons all need evidence.

Where platform reporting misleads the comparison

Meta, TikTok and Google report conversions on their own attribution windows, so one order can appear in more than one platform total. Comparing agencies on those totals rewards the agency that claims most generously.

Platform totals also exclude returns and cancellations, which matter more in fashion and homeware. Ask for a reconciled view against your own order data, with the method written down and the returns window agreed before the first report.

Common questions

Does an ecommerce brand need a specialist paid social agency?

No, but it needs an agency that can show catalogue and feed work on a comparable platform. A generalist can learn the process; you should not pay for that learning inside your retainer.

How should we compare UK ecommerce ad spend between agencies?

Fix one scope first: same platforms, same monthly fee, same margin target. Then compare answers to the checklist above rather than the forecasts in each pitch.

What should a Shopify brand ask before switching agency?

Who owns the pixel, the catalogue and the conversion data, and how the outgoing agency will hand them over. Put a date and an export format in the contract.