I just can't figure out what these are for. Found them in the rear footwells when I bought the car. Can't see any mention of such things in the handbook...
Somebody please embarrass me by stating what should be obvious

 

I think these are covers for the bolts holding the seat track rail to the floor, possibly 72265 and 72266 in this diagram:

 

Thanks for that, it's a distinct possibility. They're spring-loaded, by the way.

It's dark here now so I'll have a look in the morning.