if the noise stops when the clutch is depressed then its likely to be the clutch release bearing
but as this has already been replaced I'd next drain the gearbox oil and as it drains, then strain it through some paper towel to catch any debris
if you have a lot of small metal particles then its possibly a faulty gearbox bearing
If you have the inclination then you could strip down the gearbox to inspect the condition of the gear teeth and bearings
however being as you could probably pick up a good used gearbox for about £100 then its possibly the best option to find a unit with a 30 day warrenty and fit it
I'd suggest to use a Peugeot specialist brekaers to source the parts
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