This whole thing got me thinking (dangerous, I know)!
Anyway, I went exploring some more and there may be a better option. Take a look at this and see what you think:
This gadget gets plugged into your sky box/tv and then allows you to stream the tv reception (even HD) over your home network. There's software on your Mac that you use to view it. Looks pretty cool!
Tom (... and the reviews seem pretty good also!)