Thanks for all the help.
I’ll make a personal note not to reassemble in the dark!
In case it helps someone else. The TB related codes were cured by gently moving the spades on the TB to improve the connection in the plug. The misfire was caused because the breather hose on the back of the TB had come off where it goes onto the actuator. All fine now with no misfire, starting trouble or stalling at junctions!