Zen.
My ADSL2 was off the other day when I woke up, despite the OpenReach box having all the right lights. Rebooted that and my router while spending 5 minutes on hold to Zen tech support.
Who took down all the details, spotted it as a cabinet fault and said it was reported.
Two hours later, they *rang me back personally* to report it was fixed, and did I agree.
Compare that to Virgin!