Budget workbench

[Steve M]

I would second the idea of beefing up the top for rigidity. Personally I would use 18mm ply. Also consider a sheet of hardboard screwed to the top, shiny side up, to act as a replaceable protector for the inevitable spills of glue and paint.
Taking it a step further, have a look in your local Works art shop, they sell large workmats. They are not the self-healing type but they are pretty good value to further protect the worktop.