The ADSL connection mysteriously died at exactly 9am. They did the diagnostics and scheduled a lift & shift which took forever for them to actually action. On the day of the lift & shift the ADSL connection mysteriously started working again at 9am and they closed the trouble ticket with the code that says it was a customer fault and nothing to do with BT.

I got the feeling that somebody did something at the exchange which broke it and they fixed it again when they turned up do to the lift & shift.

The marking everything as a customer fault is apparently quite normal for BT even if they did actually repair something their end.