Thanks Jonathan. I saw you used steel box section for the frame of your machine. Trouble is I can't weld! I only have a gas bottle torch for doing a bit of plumbing, and I have little experience with it.

My plan at the moment is to use aluminium profile for the frame and 20mm plate for the gantry. Given the cost of aluminium profile I don't want to use it for the machine bed, although it seems ideal for easy clamping, it would come to about £300! I have some 13.7mm aluminium honeycomb panel for another project so I thought I'd use that as the bed, and then fix some MDF on top as a sacrificial layer I can screw the cutting material on to.