I was with pipex when they were pipex. when they got taken over I broke contract and surprisingly easily left them.
I re-joined Nildram who I had been with while I lived with the rents also recently been taken over and now known as Opal.
Since BT sorted out my line after giving me a dodgy one to the box in the street I've been seeing a healthy 800k-1mbit upload and a good 6-7mbit down. downloads will cruise down at 700-800kbytes at the right time in the night
I mostly use mine for gaming and see a respectable 50ms all the time. I think half the problem is the phone line. Took us months to get BT to sort it as we had noise on the line. it was a brand new house.