Thanks TerminatorX5

You know what, i can't 100% say that left/front speaker was working prior to the discharged battery, but i can 80% say it was... i know i know, i was asking my partner today, she seems to think there might have already been a problem, i was fairly certain it worked. But as you are not looking for it or listening for it at the time, i really cant say, but yes, i'm pretty sure it worked.

Ok... I did leave the battery on charge for 8 hours and 2amps (i was told to leave it on for 20 hours)
The vehicle started fine and i had a few strange things to contend with;

1. Radio and TV channels were fine, but the Clock needed to be reset (a couple of times)
2. Fuel gauge showed dead empty (i thought, here we go, i've stuffed something in the computer, but after some driving, i see it has righted itself slowly).

This is when i discovered the Speakers on the left hand side didn't work

I am an Electrician and have all the tools and meters to test.... apart from a Battery Load Tester.

I am aware of the hidden menu in the MarkIV Computer, but i wasn't aware there is a voltage check? test #9? any hints on that?
Removing surface voltage? Sorry, i have never heard of such a thing... but willing to learn.

Yes, it is very strange the volume of the left/rear speaker should fluctuate or stop, it does seem to point directly to an electric component board.

I would not all be surprised if a new battery corrected my problems, these BMW X5's sure seem ultra sensitive to voltage and current delivery.