Goto your ethernet cards properties.
scroll down to tcp/ipv4 then select properties.
Have "Obtain an Ip address automatically" selected.
but have "Use the following DNS servers addresses"
and put in 126.96.36.199 & 188.8.131.52 (OpenDNS).
This will point your browser to the above DNS servers to change a URL into an IP address, so if you are having DNS problems with BT this should sort it.