Watch out for wasp nests in your loft. They can range from the size of a golf ball to a football. Provided the wasps are not causing a nuisance they can be left alone to get on with their business. At the end of the season the queen will abandon the nest and hibernate elsewhere. The workers normally die off each season. The queen will restart another colony next year but it will rarely go back to its old nest.
This was a whopper - I wouldn't have enjoyed being in the roof space when this was live!