When you can buy a 160GB dual tuner Freeview recorder for well under £100 why bother?
For the cost of a HTPC you could get Sky+ or the Virgin equivalent and a year or more worth of subscription fees to channels that might possibly be worth watching.
I did have a 'HTPC' for a while but gave up as the Wife refused to get on with it.
As for the virgin media and sky, we had sky for about 2 years and was un-impressed with their signal quality and customer care.