superfast fibre broadband != cable. they are seperate, literally, cable networks are completely independent. if they offer you a service in an area without physical cable, they will be using the BT fibre/copper links which will be the same regardless of provider. however they can have their...
if the cable isnt really cable, but ADSL provided by a cable or other telephone company, then changing to statelite isnt going to change your broadband much. obviously you can get the Sky TV without problems, though alot of the add on items are internet based so will be suseptible to any line...