These pictures are from Wolstonbury Hill yesterday and I'm pleased to see the Digger wasp, Mellinus arvensis with a Common wasp and numerous species of flies of all sizes.
http://www.david.element.ukgateway.net/hymenoptera23.htm for some amazing photo's of this wasp. On the same flowers was a Wasp eating spider(?) last week. click here to go to that entry on this blog.