Queen wasps build new nests every year and old nests to not become occupied by other wasps so if you have a nest in your loft that is bigger than a tennis ball in the first few months of the year it is most likely an old nest and can be removed by yourself. Seasons change annually but rule of thumb is Bees appear first followed a month or so later by wasps. We do not eradicate bees, their nests or swarms unless they are a public health issue.