A local birder posted an image on a local website, expressing the opinion that it had to be a Rough-legged Buzzard and asking for comments. Despite responses to the effect that this was a Common Buzzard, the OP appears not to have changed his opinion. I would be interested in comments from the forum. Image taken in Milton Keynes, UK, on or around April 20. Link to image:
http://www.goingbirding.co.uk/bucks/show_photo.asp?status_id=8&speciestype=2&photo_id=6218
http://www.goingbirding.co.uk/bucks/show_photo.asp?status_id=8&speciestype=2&photo_id=6218