Thanks for your info CB (and everyone else of course)
the airport where the light came on is a very helpful one, we get our fixwing a/c maintained there which was v. lucky!
So I left it there and have a company called Helli Holland coming down to look at it. I spoke to the guy I bought the helicopter off and he is getting a new or o/h tr gearbox and he is going to fit it to the helicopter.
Thanks for help again.TD