So the BT engineer finally came and seemed to know what he was doing. He used his fancy equipment to work out that our line was totally dead and that the fault was a very short distance away, at a nearby junction box, only a few hundred metres from the house. (635 metres to be precise!) Of he trotted to see what was wrong and returned in a short time saying that the problem was a missing jumper. This is something fairly crucial that had been removed in error or by accident when some other work was being carried out. Without it we had no telephone line. He replaced the jumper and hey presto, the phone and internet were working again.
The whole process took less than an hour once we had someone sensible to talk to. I don’t know whether to be happy or cross, but at least normal service has been restored. If BT could have sent this bloke to sort the job out straight away we could have been saved from a lot of angst and aggravation, not to mention inconvenience.