Well, you'll never believe it...
Sorted!!!!
As of this morning I am registering 80/20 from Cabinet 19!
To say I am ecstatic is an understatement. 6 months of pain to get here.
So after all that how did it happen? Well, getting that new line in certainly helped. I then contacted the stormtroopers at AAISP as a few had suggested, and within a week they had it addressed. I have been advised that it was a records issue and contact was made from AA to BTW who in turn contacted Openreach and got the thing sorted. I got an email this am, and by 11.am the DSL checker was showing a full 80/20 service from the new Cabinet 19. I had actually got to the point of snarling at that cabinet each day as I drove past it. A painful and cruel reminder of what I was missing with its big coloured "Fast Broadband now available" poster on front!!
So what can I say? A massive thank you to AAISP. I won't name the chap who helped but he is a superstar. I am now in the process of changing service to AA. They are a bit more expensive, but if this is the level of service provided, it will be money well spent.
Lesson learnt. Never give up. It seemed that I would never get this addressed, but if you escalate things methodically and work through your options you will get there. In the meantime, I have contacted the Ombudsman again re shambolic Talktalk, and I am not resting until they take action over the nightmare they put me through with this.
So hopefully in a few weeks Ill be all fibred up again at hitherto unseen speeds!
Many thanks to all who contributed to this thread. Your advice has been very helpful and I will keep coming back for hints and tips.
Good luck.