Here's another view.....

 

Screw them in from the other side. Only one side will be threaded. The screw goes through the plain side, through the link and into the thread. That's what it looks like to me

 

I was lying in bed, lights off, half asleep when I heard the email arrive in my inbox that someone had replied to my thread. When I read your post Murray I thought "Mate, I told you it was stuck. I can't get it out let alone screw it in from the other side." But then your comment made me think to screw another bolt in from the other side to push the stuck one out. Done! Turns out I screwed them in from the correct side but I must have over done it and warped something. It seems these control links need to be left quite loose to get a smooth action.

Thanks Murray! You're my new best mate!