Just to clarify, did you really mean Bluetooth or did you mean to say WiFi ?
I really wouldn't recommend trying to use the internet over Bluetooth, it may bring on your early demise !
If you indeed meant to say Wifi, doesn't the BT Infinity home-hub come with that built-in as standard ?
Taking a guess here, what you probably are after is a WiFi access point for another spot in your vast mansion where the signal is poor ? Am I along the right lines ? In which case, I must congratulate you on having the foresight to have run CAT5e cable around your castle ... because that will make your life a lot easier in trying to properly implement local WiFi hotspots in different areas of your castle !