I forgot to say that the gearbox has been fully reconditioned not all that long ago, I also put in a new clutch plate at the same time.
I will check the oil level and go from there.
But the noise doesn't get louder as you rev it or anything.
Thanks guys for your comments

might be the bearings in the gearbox

mines doing the same thing and gets worse as the car revs, kinda sounds like its coming from alternator

check your oil level! The A12 box in the thou started screaming when i rean it dry

Topped it up and its all good now

is it a sound like a fan spinning or is it like a old kettle boiling, if its like a kettle boiling maybe check for oil leaks aswell

Hi everyone,
When I drive my 120y, I can here a slight whistleing noise, it's not all that loud and it does it in all gears including neutral, and it doesn't matter if the clutch is in or out either.
I jacked up the rear today and started it up in first gear and let the clutch out to get enough speed for the wheels to spin so I could hear the noise.
It sounds like it's coming from the end of the gearbox where the tailshaft goes into.

Has anyone struck this before. Cheers