It flew at me last night (I could hear it buzzing). It was perhaps as much as an inch long. It landed on its back and couldn't get up (it is on its back in the picture). I think it may be a similar insect to ones I saw last year swarming around a tree in the garden, on an evening, around sunset (but not during the day). The picture is not great, but was the best I could do with the camera to hand. It looks (to me) to be somewhere between a bee and a beetle.