So an update to this.... saw my dad and tried to do a drain test... which was somewhat inconclusive - (with the multimeter in series) the drain was very erratic...(jumping from 0.25A to 4.2A) ... becasue... the interior light was going on and off and what sounded like the door solenoids clicking on and off continually every 5 seconds or so.... no stable reading and no idea why the light and (door??) solenoids were clicking... really odd. With the multimeter removed and the battery terminals reconnedted as normal, there was no erratic behavior from the interior electrics.
However, I think the problem may be something else, as he said that
the battery warning light on the dash has now started coming on occasionally when driving....

I tested the battery voltage/charge with the car running when at idle and it only showed 12.6v.... dropping over a period of 30seconds to just over 12v. After applying 2K rpm, it rose to 13.2V.... and then slowly kept dropping even at constant rpm. The battery light on the dash would go off.... then on again.... then off when more revs applied....
So it seems like an alternator issue? OR would this be caused by the regulator?
And if either of these.... can I source an inexpensive one for him? Is the regulator a big job/how-to available?
Thanks as always gents!