Give the old Sky box the heave-oh. Freesat will be transmitting shortly. Receivers cost around £30 or £90 for the HD version and what's best... NO SUBSCRIPTIONS. Connect it to your existing Sky dish, (you may require a replacement multi-LNB, double or quad output). A cost effective way of bringing in HD television without having Sky.
Receivers available from many outlets and eBay (the prices will no doubt rise when transmission starts)
Sky... You're Fired....