You could run a long HDMI cable from a HDMI video card connection on your PC, if you have one available, to connect to a HDMI TV connection. A 7M cable is approx £25. But, not sure how you would easily go about controlling the PC remotely when watching the TV
A more elegant option is to purchase Dual Wireless link TV boxes and connect one box to your PC and the other to the TV. Some of these type of units come with a Scart socket so you would need one on the PC or maybe a SCART / AV convertor adaptor. Take a look at:
http://www.ebay.co.uk/itm/PHILIPS-SLV3100-Wireless-TV-Link-SLV-3100-No-IR-Lead-/261145575081#vi-content
Some newer models on the market offer HDMI connections also, but are most likely more expensive.
But, not sure how you would easily go about controlling the PC remotely upstairs when watching the TV!
If you have a sky+ hd box you can get iplayer from the Sky service which would not require the PC!