Well I now have a rolling chassis although I had some obstacles to overcome on the way .

The worst problem was that the motor ran faster in reverse than forward so after much internet trawling and forum searching I still couldn't find the answer .
So when the lightbulb moment hit I couldn't wait to try out my cure .
All I have done is strip down the axles again and open up the diffs and turn the crown gear around and put it all back together.
Perfect runs just as it should do faster forward slowly backwards .
All happy again.