Box1 has its visitors too. The nesting material you can see here is from last year as this nest was deserted by the female just as she completed the nest. I have had a look inside the nest box and the material is clean and dry, but I think I should remove it anyway ready for a new year.
Some people argue that bluetits that find their own nest sites will almost certainly use sites that have been used before. However, you cannot contest the fact that removing the old nesting material and scalding the inside of the nest box improves the chance that the nest will be parasite free.