Thanks for your suggestion Larry.
I did actually resolve the issue by an extremely convolute process of recreating the .dxf from the GCode then recreating the toolpath to 3 decimal places.
There must be software, similar to Graham's Metric to Inch to Metric converter, which could do this task in a fraction of the time but I was unable to find anything suitable. Still, problem resolved now thanks again.
Tweakie.