You haven't told us the year of the car.. The one on the Peugeot forum was four years old, and even with low milage the cam belt needed changing. Age does weary them and age condemn. The noise which we can hear on the Youtube video does sound remarkably as though there's a tooth failing on the cam belt. Generally, a squeaking auxiliary belt is quite obvious and more of a solid 'squeak', 'squeak', 'squeak', whereas what we hear in your video is a sort of tinkly squeak which sounds like a cam belt tooth interacting with the toothed pulleys. On a badly perished cam belt, you can pull the teeth off with your fingers. For certain, you won't find the noise until you take the cam belt cover off. The other thing which can make this sort of noise is the auxiliary belt's crankshaft damper pulley, when the rubber between the inner and outer parts starts to fail.

As for the Peugeot forum, the chap said that the garage proved the auxiliary belt was not the cause of the noise by spraying it with WD40. Now I can understand spraying it with belt dressing, but if the belt didn't need changing before, it certainly will after being sprayed with WD40!