Have you made sure that the router has "assumed" the MAC address of the computer that was used in the broadband installation.
Blueyonder only allow web access to registered MAC addresses. When you set up the broadband, the computer that was connected directly to the cable modem is the registered computer (and MAC address).
When you set up the router, tell it to use the MAC address of that computer. This means that at Blueyonder's end, it assumes that it is just that computer accessing the web.
If that doesn't work then you need to post more details about any other computers on the wireless network (I'm assuming there are more than one as you have said "MAC Addresses") or any error messages you are getting.