That's it, thanks!
Unclenick, the original screw was long lost before I bought the gun. The one fitted didn't have the serrations, and was glued in place.
The rest of the parts are there, both springs, the detent pin, the pivot pin is solid rather than rolled. But whilst searching for the part I found plenty of forums advising replacing the rolled pin with a solid one, so I'll leave it like that.
It moves freely, just needs the screw.
Follow up: Having ordered it, I was looking around the site and discovered there are three of these, different numbers. My gun is a Gold Cup Nation Match series 80, so I should have ordered 244320c rather than 'a'. I've emailed them about it, hopefully they can change the order...
I wonder what the difference is.
