London's Guide to Hiring the BEST Instagram Ads Agency

Trying to find a decent Instagram Ads agency in London can feel like a proper nightmare. You're bombarded with agencies in slick Shoreditch offices promising the world, big-name firms with flashy client logos, and countless freelancers all claiming to be the next big thing. The truth is, most of them are average at best. They talk a good game but fall back on generic strategies that burn through your cash with little to show for it.

The problem is that London founders are often sold a lie. They're told to look for an agency with a local presence, impressive-sounding jargon, and a big team. None of that actually matters. I've seen businesses waste tens of thousands of pounds on agencies that were just a few tube stops away but had zero real experience in their specific sector. The key isn't finding someone nearby; it's finding someone who deeply understands your customer and has a track record of reaching them profitably. This guide will walk you through how to do just that, cutting through the noise to find a partner that can actually grow your business.

So, why is it so hard to pick the right agency in London?

The London market is saturated. You have the massive, old-school network agencies, often based around Soho or the West End. They have huge overheads, which you pay for, and you'll likely be handed off to a junior account manager after the initial pitch. Then you have the thousands of smaller, boutique agencies. Some are brilliant, highly-specialised teams. Others are just a couple of people who've completed an online course and are learning on your dime. It's incredibly difficult to tell them apart.

The core issue is a misalignment of incentives. Many agencies are focused on signing you up and hitting a certain ad spend level to justify their retainer. They're not always focused on your bottom line: profit. They'll celebrate vanity metrics like 'reach' and 'impressions' because they look good on a report, but those numbers don't pay your staff's wages. One of the biggest myths is that awareness campaigns are a good starting point. For most businesses, this is just paying to reach people who will never buy from you. You need an agency that is obsessed with conversions—sales, qualified leads, actual paying customers—from day one. Everything else is a distraction.

This is where you need to change your mindset. You're not just hiring a supplier to press buttons on Facebook's Ads Manager. You're looking for a strategic partner who understands business maths. Someone who asks about your customer lifetime value (LTV) and profit margins before they even mention a campaign idea. Finding this kind of partner is rare, but it's the only way to get a real return on your investment in a market as competitive as London's.

Forget the postcode, focus on the proof. What should I actually look for?

This is the most important part. Your entire decision should hinge on one thing: proof. Specifically, proof that they have solved a similar problem for a similar business before. Don't be swayed by a slick presentation or a confident salesperson. Demand to see detailed case studies.

And I don't mean a single slide with a client's logo and a vague statement like "increased brand awareness by 200%". That's meaningless. A proper case study should walk you through the entire process:

• -> The Client: Who were they? What industry are they in? What was their specific situation?
• -> The Problem: What was the challenge they were facing? Were their costs too high? Were they struggling to scale? Be specific.
• -> The Solution: What exact strategy did the agency implement? What platforms did they use? What kind of targeting and creative did they deploy? This is where their expertise should shine through.
• -> The Results: This needs to be in hard numbers. How much revenue was generated? What was the Return On Ad Spend (ROAS)? What was the Cost Per Lead (CPL) or Cost Per Acquisition (CPA)? And critically, these figures should be in pounds (£), showing experience in the UK market. For instance, one of our medical SaaS clients saw us reduce their CPA from £100 down to just £7, and for another client in the prize draw space, we generated £107k at over 600% ROAS. Those are the kind of specific, meaningful results you're looking for.

If an agency can't provide at least a couple of these detailed case studies for businesses that look and feel like yours, they are not the right fit. It doesn't matter if they've worked with a massive household name in a completely different sector. That experience is probably irrelevant to your high-ticket course or B2B SaaS product. You need a specialist, not a generalist. It's also a good idea to check their reviews to see what past clients are saying. If the feedback is consistently strong, it's a good sign. But remember, case studies are more important as they show the 'how' behind the success.

A good agency should make this process easy for you. For any potential client, we offer a free initial consultation where we'll actually review their ad account and strategy. This isn't a sales pitch; it's a working session. It gives them a direct taste of the expertise they'd be getting. If an agency isn't willing to offer this kind of value upfront, you have to question how much they'll offer once you've signed a contract. Ultimately, vetting a paid ads agency in London comes down to finding that tangible proof of expertise before you commit.

Okay, but how do I know if their case studies are genuinely relevant?

This is where you need to put on your detective hat. Let's say you're a London-based FinTech startup looking to acquire new users. An agency shows you a brilliant case study for an eCommerce brand selling womens apparel that achieved a 691% return. Impressive, right? But it's almost completely irrelevant to you.

The skills needed to sell a £50 dress on Instagram are vastly different from those needed to acquire a qualified lead for a complex financial product. The sales cycles are different, the customer mindset is different, and the compliance landscape (especially in FinTech) is a minefield. You need an agency that understands the nuances of your specific industry.

Here's a simple flowchart to guide your thinking as you review potential agencies:

When you're at step 3, "Niche Match?", dig deep. If you are a FinTech company trying to find Meta Ads experts, ask them about their experience with FCA regulations in ad copy. If you sell high-ticket courses, ask them about building funnels for info-products and what kind of cost per registration they've achieved. I remember one campaign where we took a client selling courses from zero to $115k in revenue in just six weeks because we understood that specific funnel. That's the kind of specialised knowledge you're paying for. A generalist agency simply won't have those answers. They'll give you a vague response about "best practices," which is code for "we'll figure it out as we go."

What questions should I ask them on the discovery call?

The initial call is your chance to interview them, not the other way around. Most founders make the mistake of letting the agency lead the conversation, which quickly turns into a generic sales pitch. You need to take control and use this time to truly assess their competence.

Your first clue is what they ask you. A great agency will spend most of the call asking you questions. They'll want to know about your business model, your profit margins, your customer lifetime value, your sales cycle, and your biggest business challenges. They are acting like a doctor, diagnosing the problem before prescribing a solution. If they jump straight into talking about their 'proprietary 5-step process' or showing you a flashy presentation without understanding your business, it's a massive red flag.

Here are some questions you should definitely ask:

• -> "Based on what I've told you about my business, what would be your initial 90-day strategic approach?" This forces them to think on their feet and apply their knowledge to your specific situation. Look for an answer that is tailored and references specific campaign types, targeting angles, or creative ideas relevant to you.
• -> "Can you walk me through a time a campaign for a client like me went wrong, and how you fixed it?" This is a great question. It tests their honesty and problem-solving skills. Every experienced advertiser has had campaigns fail. The good ones learn from it and can articulate that process. An agency that claims they've never had a failing campaign is either lying or inexperienced.
• -> "What metrics will you be focusing on, and why?" The answer should be tied directly to your business goals. If you're an eCommerce store, they should be talking about ROAS and profit. If you're B2B, it should be about Cost Per Qualified Lead and contribution to the sales pipeline. If they start waffling on about impressions, clicks, or click-through-rate (CTR) as primary success metrics, they are focusing on the wrong things.
• -> "How do you approach creative testing?" This is a crucial one for Instagram. The creative is everything. They should have a clear, structured process for testing different ad formats (video, image, carousel), hooks, angles, and copy. A vague answer like "we test what works" isn't good enough.

The goal of this call isn't to get a final proposal. It's to decide if they have the brainpower and experience to be a trusted partner. You should leave the call feeling like you've learned something and that they've given you some genuine value, even if you don't end up working with them.

What kind of results are actually realistic for a London business?

This is where honesty is vital. Any agency that guarantees results is lying to you. Paid advertising is not a magic wand; it's a process of systematic testing and optimisation. No one can predict exactly how a campaign will perform before it's live. However, an experienced agency should be able to give you a realistic ballpark based on their past performance with similar clients in the UK market.

Performance can vary wildly based on your industry, offer, and price point. For example, getting signups for an app might cost around £1-£2 per signup, as we've seen with clients. But acquiring a qualified B2B lead for a high-ticket software product on LinkedIn could easily be £20-£50 or even higher. I recall one campaign we managed for B2B decision makers where a $22 CPL was a fantastic result given the deal size on the back end. For eCommerce, success is measured by Return On Ad Spend (ROAS). A 300% ROAS (meaning you get £3 back for every £1 you spend) might be a great starting point, but we've had campaigns achieve over 1000% ROAS for clients like subscription box companies.

Here’s a rough guide to what you might expect for different objectives in a competitive, developed market like the UK:

The key is to have a realistic conversation about these numbers. An agency should be able to explain the factors that will influence your costs and what their plan is to optimise towards the lower end of the range. Be wary of anyone promising costs that seem too good to be true. It's often a sign they're going to target low-quality audiences just to hit a number, leaving you with leads that never convert. For London businesses, it's often more effective to pay a bit more for a higher quality customer, as discussed in our thoughts on why you should ditch the 'best time to post' mentality and focus on quality targeting instead.

How do I calculate what I can *really* afford to spend?

This is the question that separates founders who build profitable businesses from those who just burn cash. The real metric that matters isn't just your Cost Per Acquisition (CPA), but the ratio of your Customer Lifetime Value (LTV) to your CPA. In simple terms: how much profit does a customer generate for you over their entire relationship with your business, and how does that compare to what you paid to acquire them?

A healthy business typically aims for an LTV:CAC ratio of at least 3:1. This means for every £1 you spend to acquire a customer, they should generate at least £3 in gross margin for you over their lifetime. If you know this number, you stop obsessing over getting the cheapest possible lead and start focusing on acquiring the most valuable customers, profitably.

Most founders don't know their LTV, but it's not that hard to calculate a basic version. You need three numbers:

1. Average Revenue Per Account (ARPA): How much a customer pays you per month.
2. Gross Margin %: Your profit margin on that revenue.
3. Monthly Churn Rate %: The percentage of customers you lose each month.

The formula is: LTV = (ARPA * Gross Margin %) / Monthly Churn Rate

Use the calculator below to figure out your own LTV and what a healthy Customer Acquisition Cost might be for your business. This simple calculation will empower you to have much more strategic conversations with potential agencies.

Once you're armed with this number, your entire perspective changes. A £50 lead doesn't seem so expensive when you know that customer is worth £4,000 to your business. This is the level of financial thinking a true performance marketing partner in London should bring to the table.

What are the biggest red flags to watch out for?

As you go through this process, certain red flags should make you walk away immediately. Trust your gut. If something feels off, it probably is. Here are the most common warning signs:

• The Guarantee: As mentioned before, anyone promising or guaranteeing results (e.g., "we guarantee a 5x ROAS") is selling snake oil. This is the biggest red flag in the industry. Paid media is an auction-based system with countless variables. Guarantees are impossible.
• Lack of Specialisation: The "full-service" agency that claims to be an expert in everything from TikTok to Google Ads to SEO and PR. It's highly unlikely they are truly excellent at all of them. Look for a specialist who lives and breathes the platform you need to succeed on.
• Poor Communication: In the initial stages, are they slow to respond? Are their answers vague? This is a preview of what working with them will be like. A good agency is a proactive partner who communicates clearly and regularly.
• Focus on Vanity Metrics: If their pitch and reports are full of talk about impressions, reach, and clicks, but light on details about revenue, leads, and profit, they are hiding behind meaningless numbers.
• Unwillingness to Grant Account Access: Some agencies will insist on running ads through their own ad account, not yours. This is a massive red flag. It means you don't own your own data, and if you leave them, you lose all the campaign history and pixel data you paid them to build. You should always own your ad account.

Navigating the London agency scene is tough, but by focusing on the right things—proof, niche expertise, and business acumen—you can filter out the noise. This framework should give you a clear path to follow.

So, how do I make the final decision?

By this point, you should have narrowed it down to one or two agencies that have passed all your tests. They have relevant case studies, they impressed you on the discovery call with their strategic thinking, and their proposed metrics align with your business goals. The final decision often comes down to chemistry and trust.

To make it easier, here's a summary table of the vetting framework we've discussed. Use it as a checklist.

Choosing an agency is a significant investment. It's not just the monthly retainer; it's the ad spend they'll be managing and the opportunity cost if they get it wrong. Take your time, do your due diligence, and don't be afraid to ask the tough questions. The right partner will welcome the scrutiny because they're confident in the value they provide. They'll see you as a serious founder and be eager to build a long-term, profitable relationship.

If you're tired of the typical agency sales pitches and want to have a strategic conversation about how to actually grow your business with paid ads, perhaps it's time we talked. We offer a free, no-obligation strategy session where we'll dive into your ad account, analyse your current performance, and give you actionable advice you can implement right away. If we're a good fit, we can discuss what working together looks like. If not, you'll walk away with some valuable free advice. Schedule your free consultation today.