Thanks for all the responses guys. My base is going to be made of slats of imitation wood flooring glued together to size, it actually worked out perfect as far as size goes, matching the template trak mat layout sheet that came in my set, then im reinforcing with 2x1 inch timber all round and sectioned in the middle to keep it firm, its this that im thinking of resting on the table or whatever is eventually used, as its going in a fixed place and not going to be moved around once its in place. Eventually i will be extended from it as i have found that there will be more room than i hoped,but id like to keep the trak mat design as i like the look of it, also it keeps it pretty simple for me to get more familiar with everything, as im a total starter in this, never done this before.
As for the top alastairq, I have a sheet of ply that i can fix on the top, which i think would be stable enough with some bracing of the legs too?