Thanks for the informative replies. So running a couple of long belts on the outside shouldn't be a problem? I would probably use self tensioners if that'd work? I will check out Deans cnc, cheers.

Yea, I thought about access to the pulley after I did the drawing, haha. Not good. Could put a Perspex plate across the back where no cutting is going to take place, but whats the point. Could put some nice neon lights in there too,haha. :)

Would the top section of the gantry work O.K? As its easy to do, just 5 pieces of 120mmx60mm box section. Looks a bit crude but would add extra 8mm steel plate to support the top too.

Will keep checking other peoples designs as I agree with you guys by making a tried and tested cnc.

I've also seen your project 1 silyavski. Wow that looks like a beast! Very nice. But looks too expensive and heavy for what I want, also I don't think I'd be able to make something like that. Really want to keep the whole cnc less than 100kg.