I'm a bit lost too on this one-I have to say!
Full HD is based on a progressively scanned picture of 1080p, but you can still have HD pictures received from SKY HD either at 720p or 1080i depending on which format a particular programme has decided to use for transmission.
But to receive and display full 1080p HD you need a Blu Ray/HDD player and compatible resolution TV screen, otherwise you are dependent on Upscaling DVD players with 720p/1080i capability... or one that upscales upto 1080p if you're intending to buy Blu Ray/HDD, to upscale DVD's to as near 1080p as is possible on a full HD screen.
One of editors at Future Net emailed today to say that he was actually convinced that SKY would eventually broadcast in 1080p, but as I said to him that was surely more dependent on the programme makers than SKY, besides which it would also prove more expensive and the SKY subscription too would have to be increased and I'm not sure sure people will want to spend even more money for what is currently, and relatively speaking, crap TV anyway.