To see one, look in flowery chalk grassland which has not been used for farming, our commons are perfect! But they are found in other habitats such as; woodland rides and clearings, coastal grassland, road verges, railway embankments and sometimes even gardens
Marbled Whites (Melanargia galathea)
are the only butterflies in the UK with these striking black and white markings, so are hard to mistake for anything else. The main difference between male and females is that the females have a slight brown tinge to the undersides of their wings. They are found mainly in southern England & Wales and are scarce everywhere else, but they have been spreading northwards in the last twenty years, perhaps due to global warming.
For more info see https://butterfly-conservation.org/butterflies/marbled-white