6mm, cuddling up in bark crevices. In birch wood.
No interactions present.
Certainly Chrysomelidae. Possibly an Altica as the elytra look only weakly punctured (so ruling out Phratora, which are similar shape and colour), but I can't be sure without seeing the legs more clearly. They should have quite chunky hind thighs as they are jumping beetles.
Dear John, thank you for your identification. We did have a chance to take a pic of the underside but we didn't think of it!
Lat/Lng: 53.340482679688, -2.2025012969971
OS grid ref: SJ866826