Hi Andy,
Try ACTion Electronics – 19, Carisbrooke Dr., Nottingham NG3-5DS Tel:0115 9607951
or their web site http://www.action-electronics.co.uk
They do a motor/gearbox set (M7G) for radars with ratios of 9:1 / 27:1 and runs from a single 1.2 NiCad
They also do a motor components set, which allows the motor to run from a standard 6v or 12v main drive battery.
The motor hides under the wheelhouse and drive is via brass rod/plastic tube (you provide) through the house to the radar. When you paint the tube to the internal colours it is almost invisible.
Cheers – Kenny
ps – Don’t know where your based, but they also attend the boat shows. I purchased mine at the Ellesmere show last year.