Thanks a lot for your reply. I have spent some more time trying to make this work, thus the slow reply!
My original hypothesis was that the spiral piece of metal attached (by the small metal loop end) to exactly where you said it did using the black plastic piece, but I'd actually discounted it because I couldn't make the distances work out.
Do you think the shape of the spiral piece of metal looks correct in my original photo? I'm wondering if it has gotten seriously bent and thus why I can't fit it back into place.
I measured the length of the spiral piece, and then that distance from the connection point and it's nowhere near where the spiral end is!
If I force the spiral piece down towards where it's meant to go, the large spiral is approximately on top of the point where it should be mounting to the black plastic piece. If it is indeed the smaller end of the spiral piece that connects to the black plastic, then I can only guess that mine has got bent or perhaps I need to exert a lot of force which is tricky in such a small space!
Here you can see the large spiral part over the mount part.
Thanks a lot for your excellent advice so far!