Rough sounding clutch

Now I know that the citigo gearbox isn't the quietest out there but over the last few days I have noticed that with the clutch depressed and out of gear the clutch/gearbox sounds rough.

Give it a rev to about 2500rpm and it then smoothes out and sounds ok. It almost sounds like/similar to rough centrifugal clutch. Although it's probably just a noisy throw out bearing.

Anyone else noticed this?