When your Sky+ dish is installed, the "LNB" (the device that sits on the end of the dish's arm) will be replaced with a "quad LNB". This is because the Sky+ box requires two dish inputs.
The remaining two inputs can each be linked to a standard Digibox. Sky charges Â£25 for the installation engineer to run this cable in for you.
If you are considering having a Digibox on another TV for free-to-view viewing, you may like to get the engineer to run the cable in for that TV too! A second-hand Digibox would give you the ability to watch around 100 channels independent of the other two boxes.
Your existing subscription card will used in your new Sky+ box, so you can use your old Digibox in the other room. Where you can watch all the free-to-air channels (including all the BBC channels).