Our blue tit has laid eggs. It’s not easy to see as she diligently covers them up but I have seen glimpses. Below is one of the videos where at least one of them is visible. Also a rare appearance of the male in the birdbox too.
I also guessed she was laying eggs as she normally leaves the nest really early in the morning. However, recently she has been ‘sleeping in’ and laying an egg for the last couple of mornings.