I gave up and sent it over to @coldharbour in the end.
Is your frame alu or steel? it may be easier for you if so, my issue was that I couldn't grip the riv nut tight enough to remove the original bolt that was in it (as that seems to be seized in the riv nut too annoyingly) if it wasn't i'd have followed the method in this video to refix it!
It's carbon and doesn't have a bolt in, I think the insert might be more substantial than a rivnut so I am wondering if it's possible to helicoil it.. I'll need to have another look.
I gave up and sent it over to @coldharbour in the end.
Is your frame alu or steel? it may be easier for you if so, my issue was that I couldn't grip the riv nut tight enough to remove the original bolt that was in it (as that seems to be seized in the riv nut too annoyingly) if it wasn't i'd have followed the method in this video to refix it!
https://www.youtube.com/watch?v=mkTxYsdzo0I