For the speed control we will use 2 servos, one for each motor. They will mounted on a copper circuit board and be able to go 2 different speeds, full speed and half speed. Half speed is achieved by connecting 2 resistors (one for each side of the board). <- That's a rubbish description but I'll post a picture when its been built.

I'm at Brighton University and the module is taught by Ian Watts if that's useful to you.
Ah, gotcha, that sounds like a pretty fun build! Ad hoc micro-switch/servo speed control makes for quite a jerky driving style but you can probs get used to it.

Thanks for the tip off, I'll pass it on