Well, the new ladder didn't work.
I don't know if it was the ladder, or if it was poppy going broody and leaving Lotti on her own, or a combination of things, but Lotti has now taken to sleeping in the egg underneath the Cube. My attempts at ushering her up the ladder fail. She waits until I am back in the house, then comes out again.
I tried taking Florence out of the picture, leaving only Roobarb to deal with,... no luck.
So, yesterday, I started on a new plan of attack.
At shutting-in time, I shut them all in the run, but did not separate-off the Bullies. I decided I'd let them sleep where they wanted. I expected everyone apart from Lotti to sleep in the orange cube. I'm not too worried about Lotti sleeping in the Egg, because the weather is OK. However, I don't rally want it to become a habit.
At 5am I was woken up by Lotti squawking. Fearing that my neighbours would also be woken up, I went out to see what was up. I found her sitting on one of the perches, screeching her lungs out. No obvious stimulus - everyone else was still in bed. I did wonder if she had wanted to lay, but as she didn't actually lay until about 4pm today, I think this was not the case.
In my semi-sleep-walking state, I noted that the Bullies had still gone into the Green Cube, presumably out of habit.
Tonight, I'm going to leave them to it again. When it's dark, I'll go out an put Lotti in the nest box of the orange cube. I'll do that for a few days, then I'll (probably) remove the Egg.
And then we'll carry on from there.