There' are 6 HD channels available on freesatfromsky (BBC, BBC1, ITV1, C4, C5, Luxury Life) You only need the viewing card for C4 and C5
Freesatfromsky provide their own HD box (with no PVR function) if you don't already have a sky+HD box.
You won't be a Sky subscriber (so no Skyplayer or SkyGo etc.)
It's all there on the website
http://www.sky.com/shop/freesat/home/ 