There are many moths in this group, all rather similar and very hard to tell apart. To be sure about any identification you would have to catch one and spread its wings forcefully. And that is something we don't like to do. However due to the fact it was photographed in late spring (early june) and judging from the white line, the species below to the left is Agriphila tristella. The adults can be seen from June untill the beginning of October. Their wingspan is some 30 mm. An abundant species all over the British Isles in places covered with tall grasses, where the larvae live in. Agriphila tristella is a migrating species.