I received a very quick reply from Jim Swales at EdgeCam and it is a post processor issue. The fix was very easy and within EdgeCam there is an option to use IJK mode only. Once I had selected that, and re-ran the code generator, there was not an 'R' word to be seen. Now to see if that solves my problem - I'm sure it will.
Incidentally, while exploring EdgeCam a little more, I discovered that if I use 'splines' instead of 'line arcs' for the nc smoothing, I get very few arcs at all in the code but the splines are all made from very small segments. It will be interesting to see what the difference is, if any is perceptible.
Thanks very much for the pointers.
Mike