How to Choose an Ecommerce Marketing Agency in the UK

"Ecommerce agency" covers a wide range of businesses, from studios that build Shopify stores to performance teams running Google Shopping and paid social for retailers turning over millions. Hiring the wrong type is one of the most common and expensive mistakes online retailers make. This guide explains the main types, what they cost, and how to judge whether an agency can grow your profit, not just your revenue.

The Three Types of Ecommerce Agency

1. Build and platform agencies

These design, build and maintain online stores on platforms such as Shopify, WooCommerce, BigCommerce or Adobe Commerce (formerly Magento). Look for official partner status on your platform, a portfolio of live stores you can try for yourself, and a clear support arrangement after launch.

2. Growth and performance agencies

These drive traffic and sales: Google Shopping and search ads, paid social, SEO for category and product pages, and email and SMS marketing to bring customers back. They rarely build stores, and their value depends entirely on commercial results.

3. Full-service ecommerce agencies

These do both, which simplifies management but makes each discipline harder to judge. Ask which parts are delivered in-house and which are subcontracted.

Many retailers end up with a build partner for the store and a separate specialist for growth. That is often the right answer, as long as someone owns the joined-up picture.

What Ecommerce Agencies Cost

As a rough guide for 2026:

Shopify or WooCommerce store (under 50 products): £2,000–£6,000
Custom ecommerce build (50–500 products): £6,000–£15,000
Large catalogues or complex integrations: £15,000–£50,000+
Paid search and shopping management: £600–£2,500/month, or 10–20% of ad spend at higher budgets
Ecommerce SEO: £800–£3,000/month
Email and SMS marketing: £800–£2,500/month
Full-service growth retainer: £2,500–£10,000/month

Some agencies offer revenue-share deals. They can align incentives, but read the detail: which sales count, whether returns are deducted, and what happens to fees in your peak season. Our website cost guide has more on build pricing.

Six Questions to Ask Any Ecommerce Agency

1. How do you measure success?

Return on ad spend (ROAS) is the standard measure, but a high ROAS on low-margin products can still lose money. Good agencies ask for your margins and report on profit, or at least on a blended figure such as total revenue divided by total marketing spend, rather than each ad platform's own attribution, which tends to claim credit for the same sale more than once.

2. Who owns the accounts?

Your store, Google Ads, Merchant Center, Meta ad account, analytics and email platform should all be in your name, with the agency given access. If an agency runs them under its own accounts, you risk losing years of data if you part ways.

3. How do you manage product feeds?

Shopping ads and marketplaces run on your product feed. Ask how they optimise titles, attributes and categories, and how they handle out-of-stock items and price changes.

4. What is your plan for peak season?

For most retailers, Black Friday and the run-up to Christmas decide the year. Ask when planning starts, how budgets scale, and how they protect margin when you discount.

5. What about repeat customers?

Winning a first order is expensive. An agency that ignores email, repeat purchases and customer lifetime value is only optimising half the business.

6. How do you improve conversion?

Sending more traffic to a store that converts poorly is the costliest way to grow. Ask how they test product pages, checkout and site speed, or look for a specialist among our CRO agencies.

Red Flags

Reports that show revenue and ROAS but never profit
Guaranteed ROAS figures before they have seen your data
Your store or ad accounts held in the agency's name
Twelve-month minimum terms before any results
No questions about your margins, stock or fulfilment

Find an Ecommerce Agency

Of the 49 agencies on UKAgencies that list ecommerce as a service, 25 are in London. Browse ecommerce agencies across the UK, or compare ecommerce agencies in London. If paid search will be a big part of your spend, our Google Ads guide covers what you should understand before hiring anyone to run it.