Ever since I got my Clio a few months ago it's been making a sort of squealing sound when I'm letting the clutch pedal out at a certain RPM. If I'm moving off at a lower RPM (such as for downhill starts or just flat starts) it will not make the noise. It also does not make the noise if I move off at a higher RPM (e.g. for uphill starts); it seems to be somewhere in the middle, between low and higher RPM. The clutch does not seem to be slipping or any signs of wearing other than this sound; the car moves off and engages every gear perfectly fine, it's just an annoyance more than anything. It's been an ongoing problem for months and I never bothered doing anything to it or checking it out as this is my first car and I'm not looking to put any/much money into repairs. Over the months the problem does not seem to have gotten any more severe or frequent than it was when I got it.
Any idea what this is? 
Also would the car pass UK MOT test with this noise? 
Thanks