Well, this week Orange phoned me to say they were sending round a BT Engineer, which rather surprised me as surely any work needed to be done at the exchange or remotely by software. Then it occurred to me that maybe something had gone wrong when they moved my line from Orange's LLU kit to BT's WBC and any engineer could check that.
Well. 2 Openreach engs. arrived. They had not been briefed on my problem and even asked me what WBC meant . They then proceeded to test my line, fitted master socket with a filtered faceplate, replaced white box at top outside of house where overhead cable reaches house with a different brown box as being OK but obsolete and declared my line OK and not noisy. They measured Sync Speed similar to my readings.
When I suggested they should look at the exchange end and check the tie-pair (I think it's called) they said Openreach only deal with the wiring between house and exchange and their responsibility ends at the DSLAM. They agreed that my problem must be either in the exchange or in the remote settings, which are handled by some other type of engineer. They are, however, sending in a report on those lines.
What type of engineer is needed for that? It beats me why Orange didn't order the right type of engineer in the 1st place, knowing of what I was complaining. What a waste of Orange's money!