In sand dunes.
Presumably a fly gall. Similar to Lipara lucens gall on reed.
Can't find anything in the FSC book.
No identification made yet.
No interactions present.
A possibility is Aceria tenuis. You might try looking inside the gall for evidence of an occupant(s).
Single, creamy-white dipterous larva
A single hymenopteran has emerged. Specimen has been kept.
Lat/Lng: 50.785, -0.9159
OS grid ref: SZ765989