Ross, you will find a much earlier post I made on here about the radiator, gearbox issue.
I met a local guy with his Ls460
He had this issue on his Ls430 and it wrote the car off.
He had exactly the same issue with his " new " invincible Ls460 BUT he managed to save the gearbox at a cost of £3500 ( I think )
The good policy is to change the radiator stuff every 100k miles to be sure
Malc