Lyons your prob right about the tensioner, that's what Beddie means when he says cambelt. As we speak vw are doing mine. The problem lies with the tensioner not working correctly from cold, causing the belt to run un-tensioned correctly until warm. When you change a cambelt you should always change the tensioner too (I think there about £13), and if you was to change the tensioner you would have to change the cambelt anyway because it has to be removed.
If you wanted to eliminate the alternator belt simply remove it and start the car cold. In betting your noise is a whirling/cheeping/oscilating noise caused by every complete revolution of the belt.
I had to stick to my guns with vw but after grabbing the technician and having him listen with me, I'm having my work done today. If your out of warenty pop the cambelt cover off and inspect the belt for wear/tear, start the engine and keeping fingers, ties and tools clear from moving items.... Have a look as it's moving.