Thanks to jelv - confirmed that it is all bad news. I unplugged modem and then got a clear fail so I am going to ask AA to book an engineer asap, as it says
BT Test xDSL Copper Test:Fail Line test failed report fault to OR, appointment advised.Fail Line test failed report fault to OR, appointment advised. T024:FAULT - Loop (Rectified)
So a rectifier presumably implies a bad joint?
Last wednesday, the day of cwcc@a.2 installation things started to go very wrong with line cwcc@a.3 flapping from around lunchtime onwards. It seemed a bit suspicious because this was just before the engineer was due to turn up for the new line install. The next day, I did a modem swap out, decided that the modem was bad and now it seems as if maybe both line and modem were bad.
I am wondering now if the original suspicion was correct and the 'pair divert' work might have broken something. However, I don't see why that work had to be done on the same day as the house visit, but maybe it is not a matter of 'had to'; maybe the pair divert was booked, to make the job possible, and way back when, the house visit was booked to be immediately afterwards so that is why it just happened that they were on the same day.
Last wednesday was all a cockup anyway, and the job was never finished, barely started in fact. Tuesday is supposed to be the new cwcc@a.2 installation date. A thought comes to me: today it was
once again shortly before the new line install date and things go wrong once again. A pattern?