I rang them up (to report a fault on the line, which effectively was what it was) and as they could hear some crackles on my phone line, they agreed to come and check the line.... the engineer who called around to the house was really helpful and he suggested that it might need a new *box of tricks*. He did warn me that I would then have to use this new box for my pc in the future - I'd not really be able to use any of the other phone sockets for pc's.... well, that was ok with me..
Honestly, I did not flatter my eyelashes or anything like that.. BT were simply great....