Hi Marc,
I've already had belt problems twice (with my A4 AFN). The first time, the tensioner pulley was broken, which caused the belt to crumble. (It really didn't take much to break it; it looked like it was the original pulley after >220,000 km).
Shortly after (a few thousand kilometers), the freewheel pulley on the alternator seized --> another belt failed. By the way, I think this free-running wheel costs around 90 euros, if I remember correctly!
I now know that the serpentine belt drives the water pump, and that you shouldn't continue driving without it

fortunately, things turned out well again this time.
Regards,
Udo.