When I replenished my seed stock a short while ago I also purchased a nest box which was on offer at £4.99. It is an unusual shape so was interested to see what, if anything, would use it. One of the reasons it is cheap is that it seems to be designed to fix to a wall so didn't have a back. I used some scrap wood to cover it in.
A few days ago I put it up in a reasonably secluded position hoping to attract a Robin or Wren as that is the size of bird it is designed for:
Today I got Round Tuit and installed a camera to monitor any visitors. Not long after I had finished a Blue Tit was captured investigating the box a couple of times. It didn't go inside but did give the camera the once over!
If you are thinking of erecting a nestbox don't leave it until Spring. Birds start looking late Autumn and early Winter to see what is available and may use the box as a roost through the cold weather.
Every time I remember to look I can see that the Great Tit is still roosting overnight in the camera nestbox:
Standen House - dressed for Christmas
2 hours ago