If you are going to buy a new TV buy a Panasonic HD Television with Freesat built in. Freesat is a Free to View TV Service provided by the BBC & ITV and is Satellite Delivered from one of the Astra Satellites (I think it comes from Astra 2D)SKY also broadcast from the same satellites, but if you have already got a SKY HD Box I don't see much point in having Freesat or even Freeview as well, apart from the fact that these are Free whereas Sky charge for their services.
It is a choice between a Free Service from Freesat or a Subscription Service fromSKY