I then tried WMC which worked quite well with very little effort, except I can see a real lack of customization, and sound on TV3 didn't work at all. I assume it's a codec issue, though I can see nowhere I can change the settings.
I also tried MediaPortal, which worked with very little effort as well, and has sound for TV3. Apart from finding the fonts didn't fit on the buttons (which makes it look very amateur) I found it slow as all hell. Quite a few times I thought it had hung, only to find it was taking minutes to switch tasks. Is this "normal"? If so it's not tolerable.
Tomorrow I'll have another go at getting GB-PVR to work, and maybe see what I can do about TV3's sound in WMC as a temporary measure.
Spec: Q8200/4GB RAM/GTX-260/Nova T 500/Win7 x64