Thanks JAZZ

As I said I'm planning to a spec greater than I need and will not buy anything until the plan is complete, cost is the second consideration (if the plan to do what I want is too expensive it just won't happen)

It's hard to come up with a design when everything I read seems to talk in 'small' and 'large' machines with no indication what this means - if it said a rail less than 300mm is small, more than 600mm is large that would be meaningful, the words alone are not...

My main planned use is 60% keyboard cases which are basically hollowed out blocks of around 290x110x30mm - proper aluminium milling. The Z axis is big to allow for drilling holes in the back and so I can add a 4th axis at a later date.

Would be good to know what of the above leads you to suggest fixed or moving gantry please, I want to learn.