Another visit to Rowney Warren to try for additional ladybird species proved fruitless except for a longhorn beetle Pogonocherus hispidulus beaten from a Rowan.
My initial identification as Pogonocherus hispidus was corrected by the national longhorn recording scheme. Although I was aware of the similarity of the two species I thought the character that I was looking for (a blunt central tooth at the apex of the elytra) would be more obvious than it was. The white mark on the scutellum on Pogonocherus hispidulus is apparently an easier characteristic to see.
Turns out this was therefore my first encounter with Pogonocherus hispidulus but I didn't recognize it for what it was!