Sorry, I know next to nothing about this type of thing 
Will I need to pass a MAC code on to Sky for the switch to work? Not sure at the moment how it applies for moving from Cable broadband to broadband down a BT line (which we have, but it needs reactivating as the line rental was cancelled when we started with NTL).

Will I need to pass a MAC code on to Sky for the switch to work? Not sure at the moment how it applies for moving from Cable broadband to broadband down a BT line (which we have, but it needs reactivating as the line rental was cancelled when we started with NTL).