Freesat is satellite and has HD content - Freeview is digital terrestial broadcasting and some HD will be/likely to be available when it is launched in your area.
I'm in the North West and we'll have the full digital service just before the end of the year, including some HD (will need a new set top box in the case of the TV, although my Twinhan PCI Freeview TV card is HD capable).
With regard to the Pannys, some will be plasma and some LCD, some will have in-built Freesat (and Freeview) tuners and others will be the latest display electronics types.
Most manufacturers provide sets in each price point (usually two to three) to maximise sales potential - the more you pay the better the TV.
Incidentally LCD sets are on a par these days with plasma and, as normal, also use less power.
Full details of Pannys at: