NTL or any of the cable suppliers seem to be fairly good. Sister is on it and never had a problem with them, good suport as well. Now and again they can have a total outage but only for a minute or two.
I have been informed that the cable with being digital is better than BT's broadband - having never had the opportunity to compare the two directly I would not be able to confirm or deny that.
Free-online do a deal via BT which is a self install at £20 a month, worth having a look at, there are set up costs though.