Hi Tony,Thanks for the input.
I managed to catch the fault with the meter hooked up. The Battery supply to the Alternator dropped to 1.6V.
A short wild goose chase later, ( I spotted a Relay marked battery that is in fact a resistor that drops NBV to 1.5V. No idea what it's for, but it confused me),and I found the fault at the multi-plug where the engine loom jumps across to the chassis, above the Gearbox. The pins were OK, the problem was corrosion at the crimp.Why they put a plug here I've no idea, because all the other cables pass straight through.
Output now 14.78V at idle with no load and 14.7 at idle with full load.
Now as for DMMs I'm going to hook all of mine up to a battery one day and do a comparative test.
Profit now a distant memory
Take care
Mark