Hi Guys,
Some further success last night. Cutting the shield wires at the micro switches made little difference, but when I also cut the shields at the stepper motor ends I think may have fixed my problem. I only have the one piece of code to run the machine on at the moment, which runs for about 15 minutes. Today I plan to slow the feed rate right down and see if I can run it for over half an hour or so to see how it performs.
Good advice hood, thank you to both of you for your help.
Stuart