Either with an Ir repeater/extender such as this .
Or use a magic eye connected the the rf2 out on the sky box. It's really meant for connecting to a second tv and being able to change channels on that tv set, but there's no reason you couldn't use it for your application.
Also, there's the expensive but more elegant option, one of the top of the range logitech harmony remotes (895,1000 or 1100) and the optional rf extender
Not wanting to state the obvious here, but remember to allow for adequate ventilation in that cupboard, or else your box will get fried.
The Sky HD unit generates a fair amount of heat with all that data processing!
bought a magic eye and works great took me a while to sort out though - need to connect to rf2 and then go in to insatallations menu ny pressing [services] then  then  then  then [select] and the menu will appear and turn the rf2 setting to on and save
Tonya, you might be stating the obvious but your reminder is most appropriate.
I have two Sky boxes "in a cupboard" connected through a Global Combiner into an 8-way Global RF Distribution unit up in the roof space. Everything has worked beautifully for several months but recently, both boxes began spasmodically failing to respond to remote control from all of the Magic Eyes but continue to work normally when remote control is pointed directly at each Sky box. I have considered and tried all the obvious, except overheating and wonder if anyone can offer any more suggestions as to what might cause this?