David, many many thanks, you have born out all my checks so far. I have also however, rigged up a smart charger direct to the battery to see what effect that has.
The red light seemed to come on when the van had been on a site, and not been moved for a few days, and with a need to put on heating as well as lighting, and of course the kettle.
I think from the readings being obtained from the battery, a new one will be needed.
Stewart and Sue Thomson