My dwindling optimism has at last been rewarded. This morning (Sunday) the phone line went dead and I thought good, something is happening (the optimist).
Two hours later the phone rang and a very pleasant BT Open Reach engineer rang me to explain that there had been damage in the town and 400 lines had been interrupted and explained that someone had reconnected me to an incorrect line. This had been put right and all was now working including broadband.
This I found was true with the exception of the broadband which allows the router to connect but does not reach the server, so presumably TalkTalk have disconnected the server from my original line.
Hopefully I can get TalkTalk to fix that.