I've had similar problems to Steve, and so have Wishy and Nickliv - all of us are (or in Steve's case, were) with BT.
All seems to be OK today though.
I sent a long and detailed message to BT to which they neither acknowledged nor responded to in any way, so it's bye bye Mr BT as soon as I get another ISP signed up.
Thanks to Steve and Schizo for their help yesterday in trying to resolve the problem.
Del