Thanks for the feed back... It's bit a chicken and egg situation, I could easily design something I can't make..... because I don't have a mill/router !! ... Challenge is keeping the design achievable, without spending a fortune on someone machine loads of stuff up for me. So those lovely fully machined parts will probably have to wait to the second build ;)

I have a layout with supported Hiwin rails and 4 carriages, with the motor spindle axis more or less between the rails in Y, looking to minimise the offset from the support to cutter axis. Some of the material/block size are a bit light at present so I'll keep tweaking the design before posting any screen shots.
Also looking how to tie the Z axis back into the gantry.