Wife mentioned that she thought the exhaust was hanging quite low on the S-Max so I went to take a look at it and sure enough, it was ridiculous. Turns out that the support bracket that holds the exhaust onto the rubber hanger has rusted away from the back box itself so it's basically just flapping about. No holes or anything in the back box (but it has had an advisory for corroded outer skin for a while) but I very much doubt anyone would bother welding a new bracket back onto it. Ended up tying it up with lots of metal wire so it's at least in place now until, hopefully, I get a new back box on tomorrow.
Another option could be to just use metal cable ties to hold it in place as I'm sure that'd be ok for a while but I might as well get it sorted properly I suppose.