If it was me I'd use the double homeplug in CC's second Amazon link (you can get them in Argos for the same price - http://www.argos.co.uk/product/5742734)

Plug one into the wall next to your router (don't plug into a circuit breaker extension lead or it won't work) and plug one in the room with the tv etc. Connect one to the router with the provided network cable.

You will also need a second router for the tv room to create a new wireless network. You will then have a wifi networks in both rooms. They are not expensive. This one in Argos is £20 http://www.argos.co.uk/product/1227291

Then connect your TV room devices to the new network.

That's the best you will get unless you run a cable from the main router across to the TV room and then add the new wifi router. The broadbandbuyer link in my first post will supply a £50 disc as well (either that or the £20 device from argos)