Thanks.
Scanned multiple times by Enthusiasts, garages and Audi who even sent scan data to Germany, never picked up anything. Didn't stop the Entry & Start Authorisation (J518), Ignition Switch, Energy Management (J644) Control Units plus a Battery being changed out. Audi also confirmed the starter motor ok.
I'm a DIY enthusiast but my ability & knowledge stopped at rebuilding Rover 2000 TC engines, gearboxes in the 70's, Rover SD1 V8's from the 80's and Granada's in the 80's. I bowed to the greater knowledge of today's electronics since I can't argue with it until all else fails then maybe try some of the old school stuff.
Just pleased to get the fix. This forum was the most helpful with the document files and personal experience, which increased my knowledge immensely. Thanks again to all.