Scrap that last post, after much deliberation i have decided to go for the dx5e, its not really that much more expensive and other people seem to have success with it. Also the design and specs of the machine have changed slightly, parts will be on order as from friday so pictures will follow.
The new design is as follows..
Going for a 10mm hdpe baseplate and top lid instead of nylon as recommended
Sticking with the gr02's for now although ive spotted 3 cordless black and decker 12v drills on ebay, two of them are identical which could be used for the drive and the other i would use as spares and also use the gears to change the other two to all metal gearboxes.
4-5mm stainless wedge, at some point will switch to hardox if necessary.
Decided that a nylon chassis could be prone to cracking if hit by a powerful spinner, and i don't really want to use hdpe as a structural material, so the sides and back will be 10mm ali or steel with hdpe and polycarb on top of that, it might seem like overkill but i'm planning on making this thing as small and as strong as possible.
Still undecided on whether to use the botbitz 85a or 30a speed controllers.
And finally sticking with the two 8.4v 3700ah nimhs, for no other reason than i already have them kicking about and it seems a shame not to use them.

Phew that's a long one, once again all suggestions and comments welcome