Pack of 10 about £3 and crimping tool just under £8 both from that company. Have just ordered both for future work.
Final post. Yes got it to work without BT's £15 adapters and ignoring the BT Engineer's advice that it couldn't be done unless you're on fibre. So in summary I disconnected the extension wiring from the Master Socket and plugged it in to the back of the router via a twin splitter - the other socket being taken by our main cordless phone. The extension was old round 6 strand and reading that it was not good practice to crimp a 431a plug on the end, I bought a punchdown IDC connector to join on a modern 4 strand cable + 431. I got the 4 strand reversed in the connector so it wouldn't ring but soon solved that.
I am sure some expert will be along and say I've done it all wrong, but there you go. Thank you to all who offered advice.
@MissMoppettwrote:
I am sure some expert will be along and say I've done it all wrong, but there you go. Thank you to all who offered advice.
Nope, but will say 'I told you so' 😀
Thanks for the update.
thank you for posting back confirming the advice given by the forum members was correct and works solving your phone problems