Good shout Gary, I've got a fair few spare relays kicking about that I can try that with. I thought it might be the relay since the green light was still on but having not used them before, I couldn't be sure.

Calum, it's an Okin Deltadrive I bought the actuator off Alex Marler a few years ago now but I have no idea where he got it (eBay perhaps). I looked at changing the motor to a Speed 900 for more speed/power but couldn't see a way of doing it without risking messing up the gearbox.