Your router isnt tied to Sky.Your broadband provider is sky therefore YOU are tied to them.As they are your provider you need to conatct them if you want to leave and go elsewhere and obtain a MAC code.
Mattk - The Netgear routers provided for the Sky broadband service, are specially configured, to identify with Sky. Possibly, tock24 has one of these but doesn't want to stay with/go with Sky and wants to modify the router by flashing with Netgear firmware.