I've used BT for years and although as Andy's said their broadband speed varies depending on the area you're in, they're pretty consistent, and I've had no service interruptions for years. Their customer service was once excellent .. but now it's been moved out of the UK is pretty tricky when you're trying to deal with technical things when you have limited geek-speak and they have limited English and work to a script for predictable problems. Mine was when we were setting up a new computer, and it was impossible to get them to answer our questions .. although I finally found one CSA who was really helpful, spoke excellent English I could understand, and gaveme his email so I could contact him if I had another query .. and when I did he phoned me back within an hour :)
I'd love to go with Virgin .. or any cable company offering a full phone/internet/TV package, but they stopped short of my side of the city when laying cables when govt subsidies stopped, and I don't expect to ever be able to use cable
Sky seems expensive. Just wish BT would finally feel the need to compete with a full service like Virgin's.
Caryl