Do you have any opportunity to run cat 5 around the house as you mention you're thinking of 'in the future' and therefore it would make more sense to run Cat5 than coxial cable
You might also want to consider different options other than traditional sky boxes in each of the rooms
For example....
I've a 3 story Victorian house that I renovated and hence floodwired with CAt5 and put Coxial in each of the rooms and I hardly ever use the coaxial
I have a Sky HD box in my cellar fed around the ground floor of the house using 10m and 15m HDMI cables to a HDMI switch in the cellar
I've a Dreambox HD with another Sky multiroom card in the cellar which connects to the HDMI switch so can be used ground floor via HDMI cables
Then the really interesting stuff....
I have 3 x XBMC - 2 x Original Xbox and 1 x Windows XBMC all of which can select channels and stream live sat directly from the Dreambox which only require an ethernet connection - No coax/direct sat feed. Plus I get 100's of other advantages to running XBMC over and above the sat TV
Then another Dreambox which sits in another room which has direct sat feed which allows viewing of channels independant of what is on the DM800 or the Sky HD box if that makes sense
Sorry for going on but my point is that Cat5 might be the way to go and there are many alternatives to having a sky box stuck in every room