GOOD NEWS (In fact GREAT news)
My RNS E is now fully functioning and working as it should.
Guess what I did to fix it?
ABSOLUTELY NOTHING !!!!!
I decided that since all of the wiring (including the speed sensor) was as it should be, and the coding of the Sat Nav was exactly as it was before, there could not be anything else that could cause this.
So I had clutched at every straw there was to clutch at, except one!! There was only one thing I hadn't tried and that was to simply drive the car for long enough to allow the system to calibrate its speed.
After 10 minutes of driving, it was still not working but it suddenly changed the location to the right road, then froze again. After a few more minutes it again moved the position to the correct road. Bit by bit it was correcting itself and becoming more and more accurate.
After 30 minutes it had finally started acting as it should.
So now it is once again, fully operational.
I new that the car would calibrate its speed, but the VCDS instructions state that you have to set the circumference of the tyre size to 0 to force a recalibration. The controller would not accept a size of 0 (so effectively the VCDS on screen instructions are wrong when dealing with an A2 / RNS E combination).
I used the tyre size calculator to enter the correct circumference in mm and thought that was it. Because I didn't enter 0 I had assumed (dangerous!) that it would take that measurement and it would not try to recalibrate.
That was my mistake.
It was compounded because of the way that the car position was frozen and I assumed (again) that if it was merely recalibrating it would still move at least, but no.
So the cure was to just drive the car for 20 minutes or so, and because when it was not working I was merely driving around the block a few times, this was obviously not long enough for it to calibrate!!!!
This is a huge relief because I was starting to doubt my own sanity.!!
Nice to have a happy ending (no cost too)
Steve B