Luckysmum, I wouldn't start changing anything yet. Just give them some time to get used to it. The weather is so mild, it really wouldn't bother me if my birds preferred to roost outside (I don't shut them in their house, their run is enclosed). Maybe they are squabbling about who sleeps where and that is why they weren't in there? I'd give it some time before making any changes in their digs.
Oh no Paul is making changes as I type. I won't say anything to him. I didn't think of squabbling, but of course we changed their home, 3 chickens were rehomed silly me.