Bare in mind that if you go for brushless drive then you've got to make you own gearboxes, and because its brushless you will need a huge reduction, either 2 or 3 stage. To do that you at least need access to a decent pillar drill and be really precise but ideally you need a milling machine to make the gearbox plates. I would guess you are looking at at least £75 for the gearboxes assuming you go for the reduced price gears on technobots.