If the OP just wants to get his fast internet to his Smart TV for streaming things like Love Film for example (which is what I thought he was asking for) then the powerline adaptors are perfect
If he wants the actual BT Box situated by the slave then yes, he'll need a cable!
They do get warm after a while, I just make sure I switch them off before I go to bed, although I have left them on a few times with no issues.
Be aware that you can get different models that have different speeds and some have passthrough so you can still use the power socket for something...
I use these puppies
http://www.amazon.co.uk/TP-Link-TL-PA511KIT-Gigabit-Powerline-Adapter/dp/B005FVOKM8/ref=sr_1_13?ie=UTF8&qid=1372959354&sr=8-13&keywords=tp+link
Plug one network lead from the BT router in to this next to the master socket, and plug the other anywhere in the house where you...