I use BT - I am fortunate to have my service free of charge because I work for the company.
That said, they are acknowledged as being one of the best for value - their coverage and service is premier because they are the biggest, and they are the innovators of broadband.
There are cheaper providers, but as in most things, you get what you pay for. A cheap service that crashes is no service at all. I have had minimal issues with my broadband since I have had it, which is since it was available.