A very simple (pilot friendly) overview of the A320 Hydraulic system. It may just help you to see how much redundancy is built into the thing and how not worried you should be. The general idea put forwards by other posters sounds about right though I'd caution anyone to make any assumptions based on what they heard. However the one Hyd fail PTU overheats other system sounds about right.
A320 Hydraulic System Overview (Sorry I'd embed the image but it is huge and I have no idea how to scale it down on PPRuNe)
I'd also add the holding may have been to burn fuel off to escape having to perform an overweight landing, given that on 2 HYD systems the urgency to land is removed.