Or use one of these 

Hi there

I always take my sky+ with me in the caravan, as the dish I have only has one LNB, you can only record the channel you are watching also, if you have series links on the box it may put up no satellite signal being received.
Sky do supply the £20 cards but the sky+ features do not work, also they will wipe all your recording from your machine, sky also allow pairings to different boxes.
I have all my music, photos and movies on a Seagate 2TB hard drive which I connect to the tv via an N box (£18 off e-bay) which turns this into a very mobile entertainment centre,which works for me in the van or if on hols abroad via scart or hdmi connectors the N-Box all works of sd card and usb pens etc, its got its own remote control as well. WAMMG