[JasonB]

I've done this in layers.

Layer 1 is the track and the boards. The pit 'straight' is a bit freeform to fit everything in, but the back of the track exactly matches the track layout but 500mm wide. All of the boards should be possible to cut from an 8x4 sheet.

   

Layer 2 is the grass and the buildings.

   

And Layer 3 is just a bit of fun, which I couldn't resist.

   

Fingers crossed that you haven't made any more tweaks...