Mikel, I will go with Comma as I think it is a bit more 'old school' and I've read so much stuff on the internet about gearbox oil (and philpotts words of warning about fully synthetics) that I'm inclined to play safe with the GL-4 semi-synthetic.

Will have to wait until the winter now as I'm trying to use the car more often at the moment. HTH

Edited to add this useful article including comments in the red box re: The Lubrication Issue.