Thanks for the comments, I haven't really thought about the electronics but like the idea of the Leadshine AM882 drives but I'll wait until the machine is built or at least fully designed so I know what I'm trying to move around. The design keeps changing and developing but now that I've got the rails at least the size is fixed.
The rotating ballnut has intrested me but seems to add another layer of complexity that may not be needed if 10m/min is possible with BK blocks.

Jim