[Note added 2009-12-17: I now think these are probably Phasia obesa, (Diptera: Tachinidae). This species is rather small and lacks the long spines on the abdomen that Tachinid flies usually have. See photos by Chris Raper here, here, here and here.]
From a couple of weeks ago, one of two flies I noticed on agrimony (Agrimonia eupatoria) seed heads. I think they were Muscid flies (Diptera: Muscidae) because of the pattern of veins on the wings shown in one of the photos below. The following photo shows the same individual as above.
And the following two photos show the second individual which was on another seed head.
Photos taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2009-10-04.