The problem seems to be solved !.
I did contact BT and yes, the lady who rectified the issue was very competent ( interesting to watch a remote control operation taking place ) plus I also downloaded an OE repair tool.
With regard to BT however, it's the operation as whole I loathe ( and certainly anything to do with their interpretation of "customer service" ...such as the "one off" adjustment to my recent bill for reasons which are fatuous at best...but which will, quelle surprise, generate quite a lot of revenue for them and the customer has no choice other than to pay...no consultation of course, just the usual arbitary decision ) hence my reluctance to involve them.
Finally, my thanks to ALL who offered me advice....
....I learnt a lot more in the process as a result, albeit basic stuff to many no doubt, but new to me.