I'd remove that plastic trim over the rear cross member and see what's lurking underneath. The top of my cross member had gone when i started to poke around there.
I never have the time for that. CR120105L Circlip, the washer is a bog standard M10 so maybe an M10 circlip will work 4U.
I always purchase a parts book as soon as I buy the vehicle, if available that is, it gives me a better mechanical understanding of the vehicle I own, and as I started this before the www and Google that's the way for me.