In a lot of areas, it won't make much difference changing provider, because the signal is coming through the same wires. So if you're a long way from your local exchange or the wiring between the street and your house box is poor, you'll never get a good, reliable broadband whoever you use.
Obviously, in some areas, there are different options, such as Virgin media with their own wired fibre network that doesn't use the normal telephone cables.
We're stuck with the BT/Openreach cabling - there's no Virgin nor other wired infrastructure, and we're also just about the maximum distance from the BT exchange. So we're never going to get top fibre speeds. We've had broadband with talk talk, sky, and a couple of other providers, but the speed has always been poor and we suffered the connection dropping out several times per day. Despite reporting the slow speed and drops to each provider, nothing ever improved.
Last year, we finally moved to BT - as they were doing a cheap offer. At first, the speed/drops were the same, but we found their router a whole lot better - it reached all through the house which was better than anything we'd had before where we needed a repeater to reach upstairs. But, what we discovered by accident, was their line checking and fault reporting facilities via their website - we could do our own line checks and any faults found were reported instantly. First time we did it, a report on the line was found outside our premises - BT came out to repair it within 2/3 days. After that, we re-tried the fault checks, and another fault transpired - this time it was a broadband fibre fault, which took longer for them to fix - about 2 weeks - again not in our house. After that, we tried the fault check again and another fault was identified, this time it said there was a fault inside our house, so within a couple of days, another BT man came and changed the "box" inside the house. So there were in fact 3 different faults - that was a year ago, and we've enjoyed faster and consistent broadband since then - maybe only 1 or 2 dropped connections in a year!
Despite BT and openreach being official separate, my experience has been that having BT for broadband, when you're using BT for your landline, and the broadband is coming down BT cabling, means that when there's a fault, it's all "in house" under BT. Changing back to BT for broadband has certainly worked for us. Fault identifying and solving has been easy - all done via the BT website, so no phoning, no waiting in queues, no chasing, no passing the buck!