oil grades

[Adrian7]

Can someone help me with which transmission oils to use on a Moss gearbox (with o/d) Mark 2 with lmited slip diff - a car which
I'm new to.
Suprisingly the manual (and the chassis plate on the car) recomends engile oil for the gearbox e.g. "Esso 20W30" but this is really hard to buy - can I simply use a modern engine oil of this sort of viscosity e.g. 10W30?

And what about the diff - the plate says SAE90EP, so presumably there's no special requirement for the limited slip (I'm usre I've rea somewhere they need special oils)

Thanks

[PPV]

I have a Mk2 with Moss gearbox/overdrive and LSD axle. I was told to use SAE30 for the gearbox and EP90 for the axle as per the Jaguar service manual which I have done and 'touch wood' been fine for several years although I do not do lots of miles.
Regards.