That's wonderful, thank you both, now I know what it looks like, I reckon I should be able to make up something to fit. It looks like it is held in place by a small screw at the bottom and then the grub screw pushes it down from above to adjust the height.
I can't imagine why it has gone missing / been removed from mine, but I'm something can be done now I know what I need.
Thanks again, Neil.
