Ah hi Jim, yeah sent that multimeter back, the return process was a bit different but I hope I'll get my money back, only £11.98. (The process seemed a bit hit and miss, I'd be worried if it was a couple of hundred quid lol! As it it, no big deal.)
Anyway I ordered another multimeter @ £29 quid, so two-and-a-half times as dear, but seems (fingers and toes crossed) pretty amazing. Auto-ranging, and when you set the rotary switch it lights up the ports you should plug the leads into. So it should be idiot-proof which is good for me.
To cut a long story short I've just measured the battery voltage at 11.93 volts. That's short of the 12.8 we were looking for.
Regards from Terry.