Found this along the Roman Road early afternoon today. Thanks to Gareth Blockley for the ID - a Pellucid HoverFly - Volucella pellucens. There is another very similar hoverfly in Britain called Leucozona lucorum but I think my image is more likely to be the Pellucid - although I am happy to be corrected!
Pellucid HoverFly - Volucella pellucens. Click here for a larger image