Whining gearbox, manual

[carrera]

The green car has been a little bit whiney, especially when cold in 1st gear. Nothing like a classic Mini though

I was prepping for the MOT yesterday & had a listen while she was up in the air

In neutral I could hear it when spinning the NSF wheel forwards, but not backwards. Rather than a constant whine, it's actually more like a mechanical clicking

The noise is loudest from an area in front to the driveshaft, close to the diff rather than the top of the gearbox

I'm not looking to do a gearbox rebuild, but neither do I particularly want it to go bang. Looking through my paperwork I did a gearbox oil change a couple of years ago using the proper GM red stuff.

Any ideas ?