sorry its took so bloody long, but heres my bench with pics of the side panels and pics of the new bench under construction..
from the front showing the back board which is jus a full sheet of MDF bolted to the back, nice and strong.

this just shows the 2 levels and the 18mm mdf

i put corner pieces on to stop stuff rolling off and it added alot of rigidity to the entire thing too, defo worth doing

and the new one without its top, should be just as strong.