Thanks for trying to help Neil. I've not had time myself to try yet as it is still disconnected. It does have a lock feature that stops the engine being accelerated but that doesn't prevent the engine being started, According to the mechanic when I spoke to him over the phone he said when it was connected the car would not start and the display of the throttle controller did not light up, I can only think that the connecting wire has got damaged or the display unit has packed up caused by the work carried out as it was working fine before otherwise they wouldn't have been able to drive it into the workshop. if if was something that was a standard fitment on the car I would expect them to put it right.
I bought it direct from China for around £40 so I will probably just buy another one rather than trying o repair this one.