All fixed, turns out it was the aircon tensioner pulley
Replaced it on the weekend, and it sounds fine now.
Interestingly enough, when I took the old one off and comapred the two side by side, the bearing in the one that came of the car felt reasonable, I showed my dad and he said to spin it with some load on it, and sure enough you could feel the bearings grinding away!
Very happy, was easy to do as well!
Chris