https://www.dorsetnature.co.uk/pages-gall/g-275.html
"the galls made by the sexual generation of Callirhytis erythrocephala, glandium and rufescens cannot be reliably separated.
" Not seen this before. This sounds like it might be this?
Possibly a Chalcid. Seemed to have business on this bud group on an oak or was waiting for the other sex.