Crabronid wasp. That chunky-looking head holds plenty of muscle for operating the big jaws, which it uses to tunnel into wood. We used to see more of them before we get rid of or old rotting wooden conservatory. This one was trapped inside and was a bit sad and thirsty, but cheered right up when put on an oxeye.
You can see a cluster of three simple eyes on the crown of its head in the first photo.











