I am amazed at the problems we had when we were with Talk-Talk. Service and Customer Service degraded to early BT days. It took us 3 weeks to try to get minor service changes...they simply couldn't get their people to talk to one another coherantly, and we finally gave up and cancelled their services altogether. It is really a shame, because as of about 2 years ago, Onetel was a top-notch provider.
My personal advice: If you are considering Onetel (now Talk Talk), then run from them whilst you can.