Hold up, wait a minute.
I have a freesat HD box but you should be aware that even though you might get more channels than freeview (although I'm not sure about that) you will be missing some key ones that freeview does have.
e.g. right now there is no 5 (although that's coming this month), no dave, no 5 US, no Fiver, and a whole heap of other channels missing. Something to do with the difference between "free to air" and "free to view". Just because a channel is free doesn't mean it's available on Freesat.
Have a look here for a list of channels currently available and although it looks a lot it's mostly regional or rubbish.
It doesn't bother me since I tend to watch shows Dl'ed on a HTPC (which is why the sky subscription made no sense) but if you like some of the freeview channels like Dave then you'll be losing them.
HD is nice - but so far it's only really BBC cos ITV do b-all.
Wimbledon was great in HD and F1 will be awesome next year but you need to weigh up the pros and cons.
If you do go for it my advise is to go for a Humax box - (the HDR if you can afford and are prepared to wait.)
hope that helps