Hi Jeff, Sorry for the delay, have been busy with other things.
Thanks for looking at my XML and posting a revised version.
However the revised one did not work. Every time I issued an M3 command the spindle immediately ramped up to top speed, irrespective of what S command was issued.
Going into the Pulleys settings caused the spindle to ignore any M3 or M4 commands and refuse to rotate, the only way to get any spindle control back was to reboot the PC and the SS.
That happened every time I changed a pulley setting.
I tried a different PC, a different USB cable and anything else I could swap around or change but still the same result.
I went back to my previous XML (a later one to the one you looked at) that I had had some success with and it still worked OK, I then managed to tailor the pulley settings to get spindle speeds somewhere near to the entered S commands but I'm not happy at all with the way the SS handles spindle speeds - compared with the original PP connection it's a dog's breakfast.

Thanks for your help anyway.
Dave.