Piece of MDF 60cm x 60cm x 18mm-ish (Burnage M19)

Hi Folks, I'm looking for a piece of MDF 18mm thick x 60cm x 60cm (or can be larger) please.
Needs to be structurally sound and relatively cosmetically presentable (at least on one side).
It's for a replacement loft hatch so it will be painted to match our ceiling later etc.

If anybody has any such MDF board going spare ideally not too far from Burnage (M19 2 postcode) or Brooklands (M23 9 postcode) I'd be really grateful.

I can collect most afternoons and evenings.

*Photo for attention.

Thanks,
Tony