there is no such thing as a 12 month warranty that overrides your statutory rights, nor any limit on the Sale of Goods Act that says vendor liability ceases at 12 months.
It does depends on the T&Cs (no doubt on the BT site) that you are deemed to have agreed to by using the service.
On the one hand it could be an integral part of the service you are using, in which case they should replace it. They seem to give them out willy nilly to address non-relevant faults.
On the other hand you bought it and it has to have been of merchantable quality and last a period of time that a Court would see as reasonable for solid state electronics.
MaxDSL - goes as fast as it can and doesn't read the line checker first.
Are your kids pirates ? Limewire, Bearshare, Kazaa, BitTorrent, eMule are all tools of the trade.