Like so many, in the past I had been burned by major ISPs poor service, and went through a few smaller companies. I was with Firefly, who got taken over and went kaput leaving us without service over one Christmas. Aquiss stepped up and offered to take us on for no charge then and I decided to try it. That was about 13 or so years ago or more.
In that time, I've had precisely two outages - one for about 90 minutes and another over a weekend - neither were anything to do with their end and both were quickly communicated as a problem by their end.
When I set up with them they were more than helpful and spent quite some time offering us some help with a couple of problems. Since then they have been flawless. I have rung them a couple of times just to ask a couple of questions and each time they answer immediately. They're very knowledgeable and helpful. More than I've experienced anywhere else.
Recently I switched over to a FTTC service which was slightly cheaper and faster and the changeover again was flawless. Come the day, engineer arrive, does his business and Aquiss' login details were entereed and just worked instantly.
They're not the cheapest, but being disabled and stuck at home, I'm more than happy to pay a bit more for this level of reliability.
I doubt you could do better than them and Martin frankly is a real gem.