I put my flat screen on the wall in November using an articulated arm as its in the corner of the room. For the 3 cables power, scart and HDMI I have used a cable tidy (google it, although I got a silver 2 metre one from Wilkinsons for £4.99) which gives a single snake like and looking cord dangling. No need to unplug things etc as it comes with a little device which means it effectively zips around the cables.
These things are used in lots of offices etc.
BD