you need two face plates, a lenght of network cable, the type you get will dictate the maximum speed (achievable), cat5 is 10/100, cat5e/cat6 is 10/100/1000.
regarding the fitting, no different than routing an cable, if you're doing a proper job then you'll want chase out a channel for the cable then plaster over it. If you're doing a bodge job then you could simply drill trough the ceiling and leave the cable hanging, in-between this you've got tower clips (the type you would run a phone extension with).
Re the ceiling, the gap can be bigger than you think, so you're going to need either a large drill or something to feed the wire through a hole drilled either side, best bet is a sparky on the forum.
Personally as it's the sky box then I'd get a wireless acess point and a wireless router, the anytime / on demand wont be able saturate the wireless bandwidth
phone point -----> wireless router ------> desktop
|
|
wi-fi
|
|
|
|
|
wireless access point or router -------> sky
you basically create a bridge between the two wifi devices which is the same as running a cable, given the cost of running a cable properly this would probably be cheaper. an other alternative is the ethernet over power, this uses your home wiring as the cable.
also given the main problem you've got here is routing cables, I'd probably say off topic would be a better place (maybe).