hi, not sure how much i can be of help having only planed my first robot last week but lots of people recomend using a speed controller from ian watts (can be contacted on the forum i think). myself im using these:
http://www.electronize.co.uk/FR12VR_spec.htm
they are £30 for one but you should ask someone if they would be good for you as im using scooter motors.
i have also been recomended the planet 5 transmitter:
http://www.sussex-model-centre.co.uk/sh ... p?id=29064
but most shops seem to be sold out of them at the moment.....

also people have said that if u use the NiCd batterys that come with the drills they will run out fast.