Why your broadband is slower than advertised — and what you can do about it

If you’ve ever run a speed test and wondered why you’re getting 35 Mbps on a “superfast 80 Mbps” package, you’re not alone. It’s one of the most common broadband complaints in the UK — and it’s been going on for decades.

Why advertised speeds are almost always wrong

The key phrase in every ISP’s marketing is “up to.” Up to 80 Mbps. Up to 1 Gbps. That “up to” does an enormous amount of work. It means the number is a theoretical maximum, achievable only under ideal conditions that rarely exist in practice.

Several factors drive the gap between what’s advertised and what you get:

Line length and quality. For copper ADSL and VDSL (fibre to the cabinet), the further you are from the nearest street cabinet, the slower your speeds. A house 300m from a cabinet might get 70 Mbps; one 800m away might get 30 Mbps from the same package.

Network congestion. During peak hours — typically 7–10pm on weekday evenings — many ISPs struggle to provide enough capacity for all their customers at once. This is called contention, and it’s why your Netflix buffers at 9pm but loads instantly at 2am.

Equipment. Old routers, dodgy cables, and WiFi interference all reduce the speed that actually reaches your devices. This one is often your fault, not your ISP’s — but ISPs sometimes blame it when it isn’t.

Throttling. Some ISPs deliberately slow certain types of traffic — streaming services, P2P downloads, gaming — particularly for customers on cheaper packages. This is legal in most cases but rarely disclosed clearly.

What the rules actually say

Since 2019, UK ISPs have been required to provide customers with a “Minimum Guaranteed Download Speed” — an actual floor below which your connection should never fall. This number must be stated in your contract.

If your speed drops below that minimum for more than 30 days, you’re entitled to exit your contract without paying early termination charges. This is a significant consumer right that most ISPs don’t advertise prominently.

Ofcom’s Automatic Compensation scheme also requires ISPs to pay out automatically when service drops below certain thresholds — though coverage and amounts vary by provider.

Why complaints usually fail

Most broadband complaints go nowhere because customers can’t prove what’s happening. An ISP’s standard response to a complaint is to run a line test from their end, find nothing obviously wrong, and close the ticket.

Without data — timestamped speed tests, latency records, evidence of when slowdowns occurred and for how long — you have no leverage. The ISP can simply say your line is fine.

This is where continuous, automated monitoring changes things completely. A record of 47 occasions over three weeks where your speed dropped below your contractual minimum, with timestamps and test results, is a very different conversation.

What to do

1. Find your Minimum Guaranteed Speed. It’s in your contract or on your ISP’s website. If you can’t find it, ask them in writing.

2. Start monitoring. Manual speed tests are too infrequent and too easy to dismiss. Automated monitoring that runs around the clock builds the kind of evidence base that’s hard to argue with.

3. Log your complaints. Every time you contact your ISP, make a note of the date, who you spoke to, and what they said. Keep confirmation emails.

4. Escalate to an ADR scheme. If your ISP doesn’t resolve the issue within 8 weeks, you can escalate to an Alternative Dispute Resolution scheme — either CISAS or Ombudsman Services: Communications, depending on your provider. This is free, and ISPs are legally required to participate.

5. Consider switching. Sometimes the easiest solution is to move to a provider who actually delivers. Your data will tell you whether your problem is likely to be fixed by switching infrastructure type (e.g. moving from FTTC to full-fibre) or whether you should just leave.