guy's I would recommend 12mm ply for the face of the jumps and any table tops as anything less and you'd run the risk off people putting there feet through it when marshalling, plus would add strength too so wouldn't need as much 2x2
You could use thinner ply on the sides and buy rough sawn 2x2 which would be cheaper than dressed timber
Just and idea, I also have a trade point card for b&q so would save 10% off price and you'd get the board cut for free if you have the sizes you need
