I was with BT for years with my ADSL connection ( new build flat so cable not an option) and around December my connection also died on its arse.
My experience with BT has always been dont mess around with the middlemen and tech support and take it right to the top.
Ian Livingstone was the CEO that I e-mailed and within minutes I had a phone call from the 'chairman's office' offering all sorts of help that India tech support wouldnt do.
The end result was the same sadly and I left BT and joined sky broadband and so far no issues. Sky sorted out via an online order something that BT's chairman couldnt solve.
BT havent got a clue what they are doing...