I have now managed to remove the carriage. Quite simple with the other endplate onbolted.

It is now possible to just slide off the carriage in the opposite direction.

And voila, the carriage is now off the machine.

OK, with that done, I now need to withdraw the main screw. Whilst deliberating why the screw will not come out, I decided to remove the dials etc. All straight forward up to this point:

So, looking at my exploded diagram, I’m none the wiser. My main screw has a keyway along part of its length and the keyway insert seems to be stopping the screw coming away from the body and helical gear.

I’m also wondering if this ‘pin’ is stopping things. More deliberation and wine, I think!