Peter, thank you for the CamBam tip. I hadn't heard of it, and it looks interesting. You're certainly right about the cost of software, and I'm amazed that hobby users can afford stuff like AutoCAD at all (unless of course they hoist the Jolly Roger and sail off into the sunset with a dodgey copy).

I'll take a look at CamBam tomorrow. I suppose if all else fails I could actually write some CAD/CAM code myself; but I'm not very good at visualising things in 3D, and the thought of debugging 3D trig makes my head spin.