I watched two Pied Flys squabbling over a nestbox which was quite fun to watch. There were a number of holes around in the trees but they seemed to prefer the nestbox.
At one time one bird was in the nest box, the other flew up and began tapping the outside of the box, eventually the bird inside the box flew out and a mid air battle ensued. This happened 4 times. I am sure they have resolved residency by now.
There also should be females there by now too, and Redstarts too I hope.
"I need to find her a home, she`ll be here soon!"
"What about this prefab, nice and modern, secure door, but needs the roof fixing. Oh I`m not sure, I'll just wait till she gets here!"