well you do have this problem with ntl now really mate, since NTL bought telewest, then the company took over virgin-mobile, and decided to take the name of virgin.
So you are dealing with the exact same company really..
Some companys change over time in terms of quality etc, sad to hear yours has gotten so bad, mines spot on at my uni flat and at my parents place too, hard to imagine it being carp to be honest, if it was as bad as some peoples here id be up on the phone and cancel it and get BT line in straight away and do an ADSL lucky dip