Here it is guys... Away on holibobs in SW Wales and driving back to the site today the battery light flickered on a couple of times then stayed on whenever on overrun or light throttle but bury it and it went out.
Then suddenly there was a loss of power (because it went into limp) and electrical systems started shutting down. Pulled over, switched off and restarted fine but a light glow from the battery light. Sure enough, 11.2V but constant no matter what electrical load is put on. Drove the 25 minutes back to the site with no battery light but within the last 2 miles the electrical systems started shutting down. Limped to our pitch, parked up, switched off and (as expected) the battery was flat.
Left it for a while and tested the connections as best I can with (very) limited tools I have here and the battery recovered sufficiently to start the car but, again, only 11.5V whatever electrical load is applied.
So.... Is there a charging relay or a fuse that is worth checking? As this all happened suddenly with no warning.
I'm sure I know the answer but remember a Cavalier I had in the past with similar symptoms and it was a charging relay.
Failing that... Anyone in Pembrokeshire with tools and a spare alternator?