I took a lot of the interior out of my 1998 XK8 coupe ages ago, and I have two of these bolts that I cannot remember the location of - doh! The captive washer does spin independently of the nut. I've had all the seats and centre console out, as well as one of the door cards. Any idea where these are from?

 

Holding your rear seat cushion

 

Ah! For some reason I have non-original washer and nuts for that, so I must have lost these in the interior previously and replaced them.

Thanks!