Righto - that's the vision - maybe a little larger so may need some reinforcement underneath...
What I've got to work with:
Max dimension - width max ~ 1000mm depth max ~ 600mm.
Off to the green barn for a visioning exercise...
600 x 900 x 12mm ply ~$10
Some pipe insulation ~$4
Some dowel (forgot photo) ~$4
Must have some decent screws around here somewhere...