Well chaps. I found a major BMW dealership in Bangkok with the pukka computer analysis kit.
Net result, my light meant failure of the 'converter lock solenoid' a small and reasonably cheap component that can be replaced by dropping the transmission oil pan (without removing the gearbox).
UNFORTUNATELY, when we removed the oil pan there were a number of expensive looking bits attached to the magnetic plug (the remains of the 1st gear clutch assembly), net result, new transmission required.
Get the car back today, hopefully now fixed, we shall see.