Replying to my own message - can't see an edit button.
BT only had a 20m wait this morning and I spoke with an extremely helpful gentleman who ordered a second extender for me. He explained in detail the use of multiple extenders, so I understand how to ensure that the second one gives me the expected results. As I understand it, if you have extenders too close together it can cause issues.
He also suggested I could complain to Openreach but I don't think they have done anything wrong so, as he also suggested, I can always buy an inexpensive metal cover and fit that.
So as far as I am concerned all is forgiven.
Apart, that is, from the horribly distorted music whilst awaiting an answer!
