I have recently moved back in to Rainbow Quay after a 6 month sabbatical in Milton Keynes but thats another story. In addition, I have only discovered this forum and think its great!
I upgraded to Sky + in April 2007 and you do indeed need two signals. However, there is a simple 'box' that attaches to the wall that splits the incoming signal in to two and thus enables Sky +. No need for any cables to bedrooms or any of that nonsense. I have Sky + in the main room and normal Sky in the bedroon. The only issues are:
1. Sometimes the signal strength is not 100% and you have to re-boot. You can also install an amplifier to help here.
2. You need an unused satellite feed from the riser in your block. If they are being fully utilised you can't get it.
The guy who wired my up was Alan Kay (firstname.lastname@example.org) and he charged £150 plus vat and £20 for the amplifier.
Some day the whole block will be upgraded no doubt but for the moment this is a viable option.
Hope this helps