This has indeed come up before when Sky+ was first introduced and it is correct that you need a double-feed. The only way you can get the double-feed is:
1. Get your own dish (which is a no go)
2. Get an additional feed through to your flat (impractical and VERY expensive as cabling would have to be routed somehow)
3. Re-route the bedroom feed into your lounge
I went for the nice and easy 3rd option (Sky+ not HD) and it works fine. I then have a video-sender to send the signal back into the bedroom which works fairly well.