As for design im going with a basic flat chassis and bolting everything to it, once i got that sorted i will move onto something a bit more exciting.
That is fair enough. When I was prototyping my Featherweight, I bought one of those wooden garden stands on castors and simply screwed/sellotaped bits into that until it moved. I bought a set of similar motors which were really too small for a Featherweight but ideal for a Beetleweight so along the right tracks there.