Right guys we are now back up and working. I went to bed last night at 12 at it wasn't working, up this morning at 5am and low and behold its on. So I don't really have a clue what was done.
Thank you guys for all your help with this issue.
Glad its all up and running, is it at the speed you got before, I know you will probably have to wait for the up to 10 days for the line to stable, assuming they reset the line.
TBH, I think up to the point the Boost Engineer arrived, BT didn't believe it was an external fault, most issues have been internal ones. And where the Boost Engineer couldn't find the issue internally they realized it was an external issue, like at the exchange or in their network, my guesses are at the exchange like others have said.
As for getting answers on what the issue was, is 50 / 50, you might be lucky and get told what it was, but more than likely you won't.
Paul