Transmission noises on my series 3 are:

When coasting to a stop with box in 2nd and clutch depressed there is a whirring noise like a spinning ballrace or a playing card in bike spokes or shaking a box of spanners. Car is "out of gear" but all the components in the box still seem to be noisily rotating.

Slow to medium acceleration in 1st and 2nd there is a definite "chatter", sounds like gear teeth slapping each other rather than tightly engaged.

Hard acceleration - can't hear 'cos of the SP's!!

Decelerating in 1st, 2nd and 3rd, those spanners again, sounds/feels as if nothing from diff to clutch is in line.

Car has been back to Malvern for other warranty work and the written response to the noisy gearbox was:
"the drive train is very much part of the car. The aluminium chassis seems to exacerbate any noise from the transmission. On a BMW fitted with the same unit, they have so much stuffing around the car that these noises are not heard. I am afraid there is nothing much we can do about this. It is not a fault with the transmission and will not deteriorate over time. The 6speed gearbox has a lot of components and the car little soundproofing. Your car already has a rubber mounted differential which does make a big difference over the earlier cars."

I have not driven a similar Aero8 to compare, so basically I am living with my box of spanners as an example of Morgan Quirckiness hippy and still smiling every drive smile