Good neighbours?

It's probably a little too late in the year to be giving nestboxes their MOT, but yesterday I noticed that my sparrow 'terrace' box was looking the worse for wear. It's old and the roof had a crack in it that has to be letting the rain in.
So, out came the ladder and down came the box. Getting the roof off wasn't easy as the screws were badly rusted and when I took it off I wasn't sure what I was going to find inside; I knew it had been used last summer, but didn't now whether chicks were raised successfully.
But it turned out to have two nests inside - one a neat, little sparrow nest and another, a wasps' nest the size of a grapefruit. Quite a surprise. 
I wonder if the sparrow chicks found that all that buzzing going on next door kept them awake. Or maybe it was soothing and lulled them to sleep.