2p/min to USA???
http://www.telestunt.co.uk/ - 0845 "local rate"
Signing up to 18866 or 1899 may be even better, though the call-through (NTL) rates are not quite as good as the prefix (BT) rates
http://www.call1899.co.uk/index2.php - USA (BT) currently 0p/min (3p/call connect) - 1p/min +3p/call on the NTL call-through number