My nest box is just in the corner of my vision sitting at my desk. Constant backwards and forwards with food, both parents very busy.
Mine's a specific blue tits box. We also have another with a bigger hole. The sparrows booted the blue tits out one year, but we haven't seen them for a few years. I've emptied/rinsed it all out once too, still not happy with it. That cover plate would be a good idea, but this is concrete so I couldn't fix it on.
Sorry I stole your tits with my new luxury accomodation.