That's whats so frustrating Mick- I can't see any other way for it to go.
The barrel is keyed so that can only fit one way, the cam on the barrel I didn't even take off and I only disconnected one end of the rod!
It goes part way then runs out of travel, as if the rod has suddenly become too long!
I've decided the best solution is to ignore it for a few days. I'll go back to it after the weekend and I know it'll just fall into place

No-one will believe you...