It is indeed the Renault gearbox, the one with the slave cylinder outside of it. And yes, chances are it doesn't have to do with the slave itself, had someone press down the clutch while I was at the engine listening, and the noise fades away with the clutch engaged (in fact it almost disappears), so it is definitely clutch-related. Wasn't suspecting the release bearing at first because the noise is constant (i.e. with car idling in neutral), and I thought the release bearing was only solicited when the clutch was being used.
So I guess I won't avoid a trip to my local garage this time ... definitely not knowledgable enough to perform a gearbox-off job
