Whirring noise at idle only - alternator free-wheeling pulley?

[ScottyP45]

Hi folks, I've searched the forum but came up blank, however my new car, a 2.0 TDi S-Line has an annoying whirring metallic sound while idling at the lights which seems to go when revved up a bit, and doesn't seem to be the clutch bearing or tie in with anything else except idling engine speed, more noticeable when warmed up. Very noticeable in the cabin when heater and radio are off. The sound is light and a bit distant, but obvious once you know it's there.

I saw a video that suggested the alternator over run pulley was the culprit and wondered if anyone concurred? I have a ScotSure warranty and the car is a peach otherwise so before I go back to the garage I wanted to check with my esteemed colleagues on here first.

 

[ScottyP45]

I checked further tonight and this noise is only audible inside the car and only when the engine is idling, if it's not idling there's no sound and outside the car it can't be heard, the engine is near silent outside! Yet when everything is off, even the heating fans completely shut down, I hear like a metallic whirry jingly chirpy squeaky sound (struggling to describe it) kinda like when there's clean dishes on the rack in the kitchen and your washing machine spins silently but 2 cups or glasses are rubbing together in time with it. Could be a metal part rubbing lightly on something...anyone else had this?