Well this is a bobby-dazzler, as my dad used to say (and possibly still does from time to time (not about this particular creature, but when something was particularly visually impressive)). I came across it when looking again for the early spider orchids Andy and I had seen on our bike ride a few weeks ago. It was sitting in the yellow flower like an emerald ornament.
Entomology is mostly a mystery to me at the moment, something I look forward to remedying, so of course I had no idea what it was. The interweb is a marvellous place and within minutes help was to hand. It was suggested to be from the genus Cryptocephalus (cryptic-headed due to the head being almost invisible beneath the pronotum) and after a few suggestions followed by sleuthing various websites, I have decided it is Cryptocephalus aureolus rather than Cryptocephalus hypochaeridis which has bluer/darker elytra (wing cases (getting with the entomological jargon!)).