As daveh says, you'll likely have a quad lnb, so why not run another feed from that? It's pretty straightforward, you can get the cables from B&Q and the likes.
Sky+ with one input is a royal pain. I thought it'd be fine, but it's pretty annoying. Just had a week of it (due to moving house) and that was enough. Even with trying to leave the box on the correct channel for the recording, we still lost about half our recordings for various reasons.
If one show finishes at 10, and the other starts at 10, you're knacked. You have to manually end one just before the other starts, and so on. And if you're sitting in front of the TV to do that there's no real point in having a recorder
If you don't fancy running a cable yourself your local independent satellite chappy might be relatively cheap?