That's about spot on with the engine running, probably a bit low for the engine off voltage measuremant, but maybe your car was standing for a while when you took the engine off reading, Mark.
I am seriously considering a 80 amp/hour battery when I need to get a new one, as there is enough space to fit one.
I have a USB socket which is permanently juiced up as its connected to the cigar lighter circuit. I am thinking this is helping to drain my battery a bit quicker during the colder weather.
May play around with my multimeter and clip on ammeter tomorrow and see what sort of battery drain I am getting, maybe disconnect the USB socket and Halo's and see what difference that makes too...may have to put a switch on my USB socket if this is the case. My battery has been fully drained three times now since I have had it (only 8 months old) but if I jump start it and give it a 20 mile run, its fine again! Just need to run the engine for 5 mins every three days or the battery starts to get critically low!
Sundance