This may sound like a silly question but......... why on earth would you change the LNB on a Sky dish? The system doesn't require anything more than a basic reciever and is only licenced to transmit a one-way signal.

What advantage will you see by changing it?
(genuinely interested btw incase I come across sarcy). I actually used to work for Hughes Network Systems who designed and produced the Sky Satelitte system - and subsequently I now have lots of useless knowledge on Satelittes and LNB's.