Thanks to everyone for your help, I was not aware of the checker and it has been the means of getting to the root of my problem. Using the data I was able to confirm that my BT phone number and my actual home address have totally different service profiles.
The reason apparently is that BT have me down with 2 addresses for the same property, the one of the previous owners and mine which was formally changed with Royal Mail (as recoginsed by every other supplier or official agency) about 10 years ago when I moved in. They associate the phone number with the former owners address which obviously has never been updated by Openreach, as it does not exist, however my actual address has.
Apparently I am a very rare case however it has taken them months to resolve and they would not have done anything if I had not kept pushing. At this point can I thank two guys at BT call centre who finally listened to me and took some action. I am told that everything I suspected about my service options is correct and that within 48 hours my profile will be updated and I can proceed to upgrade.
