After a few hours of messing about the problem is solved and reason now is clear.
I have recently been creating G code files from Lcam files and it does not matter if those files were created with a registered or unregistered version of Mach 3 - 50 line restriction.
When I go back to the original DFX files and create G code files therefrom in LC these is no line restriction. I am using Mill only.
Seems like a bug in LC and makes one ask what Lcam files are for if this is indeed the cause of the restriction?
Whatever, now cooking on gas
Many thanks Rich for your input.
Regards Paul Hinson