Well today is a very sad day as after not seeing the blue tits going in the box for a week i decided to see what had happened as i opened the box the female was sitting on the nest but she was dead :(
There weren't any eggs. I'm not sure why she died but can only guess that the sudden rise in temperature maybe caused her to dehydrate or the male was sooo busy defending the territory that he forgot to feed her. what ever it was has really saddened me. I have removed her and the nest and can only hope another pair will decide to build a nest there.