I had that same problem and having a "spare" sat box, wanted to plug that in as choice one. After having seen the quality of the little USB box for the PC, (Yes, terrestrial coax type) I called the drones at Sky who for 50 quid, came and installed a new box. For a further ten pounds per month, all of the existing channels were mirrored to the new box, making it a both cheap and easy way out.
Now - if I wanted to get this satellite signal running through my PC and use it as a recorder in much the same way as Sky Plus, then I could take a line out from the sat box and line in to the analogue TV card which I put into my PC a year or so ago. That would give me ultimate flexibility, but I am still waiting for anything decent on Sky at all really, so I can't be bothered.
Other plusses of a setup like this might include being able to run TV trhough a flatscreen monitor, but in my own case, I invested in a Samsung 930MP Monitor/LCD TV which already has more inputs than a phone exchange, so my computers sit outside the loop after all. Oh - and I have another spare LCD screen as well.
Full circle, eh?
Conan