...under the driver's seat. Just sitting there all innocent like.

Ironically, I was looking for some small screws from the cassette player that had pinged off into nowhere whilst trying to remove it.

Too small for seatbelt mountings, seat mounts etc. Finally found out... It holds the RH rear of the driver's seat squab to the rear height adjuster. Two minutes fiddling and tightening later and it was back in place. Its mate on the other side was still tight as it wanted. Only found out what it was for by grabbing bits of the car interior and shaking them, hoping to guilty party would reveal itself.

J.