Cheers for replies guys
Basically I can use a brushless esc and 2s Lipo's, but can't use brushless motors and have a 20t limit.
Somewhere else someone said that wasn't much point using brushed motors and lipo's, so thought would go back down the nimhs route (only have the nicads as came with car) as did find nimhs to be good in the first car I had.
Essentially running an mtroniks rv15 with hpi saturn 20t in the mardave and an LRP ai runner reverse with 23t in the tamiya mini, both pretty basic combo's but for the car's scale and the rules, work out quite well, just need to sort out some 3000 ish minhs for both