It is the IP that you connect to the Internet to, ie 18.104.22.168 that needs changing, and they are dynamically served by Sky on connection.
As you have been told several times changing your LAN address will make no difference, except screw up your firewall settings.
What you can try is going to the Router Status page and click the 'Sky Test' button at the bottom. At one time this was guaranteed to trigger an IP change, but it may not work now, especially if you are on MER. Don't worry about the message you get back, it may even say you have no internet connection.