Thanks Rory,

Woking from this diagram. (I'll upload a pic when I get to a desktop) The RX is connected to a servo SW which is connected to the coil input of the relay. The Relay in closed position gives the motor no power. When activated via a the servo switch it switches on the battery power to the motor. To reverse the operaton there would be a second relay and servo SW coming from another channel on the RX wired in exactly way but with polarity reversed.

I have no exsperience with relays. Can you set a time the relay stays switched on before if returns to it's normally closed position?
Any examples of the kind of relay and servo SW I should be looking at would great.

Thanks