I went with DaveW's recommended 1.2mm and a sectioned design but still resorted to a hammer to get a decent bend where required, I covered in Letherette to hide the hammer marks :), I put some pictures of it on another thread.
However if I had do do the Job again I'd try using right Angled Aluminium for the basic structure so that Little or No Bending would be required, and then fill in the panels with sheets of 2mm.
