<< I want to be able to watch t.v through it >>
There are USB TV tuners for the reception of both Analogue and Digital broadcasts but you do need a good aerial.
<< I would like to be able to use bluetooth with my blueyonder modem. >>
I think Wi-Fi (802.11b or 802.11g) would be more appropriate than bluetooth, which is more suitable for connecting mobile phones to laptops or headsets. Bluetooth is used over very short distances.
<< can bluetooth pick up a t.v signal >>
Not as such. Bluetooth is a technology to connect two devices wirelessly over a very short distance. For TV reception, you would need a Bluetooth enabled laptop to connect to a Bluetooth enabled TV tuner (which probably doesn't exist).