Saw this company mentioned on the BVS website;
http://www.fun2ride.co.uk/
..some interesting stuff ! The trikes look similar to the ones retroandy saw.
Some of the parts look potentially useful for upgrading C5's. eg brakes, wheels, controller, 500W motor etc.
Would be a miracle if the 500 watt engine would just fit into the C5.
Would make it very illegal here to ::)
Wort to take a serious look into this engine