Hi Russ,
Thank you for your suggestion, but I found the cause and it turned out a lot simpler (and was probably down to me!).
Problem was here:
Under Configure- Mach- Spindle, I found the Check Box for "Wait For Spindle To Stabalize To XX%" was checked. Unchecked the box and the program ran through without issue.
Obvious now, but my machine does not supply Mach with Spindle Speed Feedback.
Nick.