Hello Matt,
I agree with you and Pete, it's a Lesser Spotted Woodpecker.
Yes, the usual caveats, but your picture seems to capture the right jizz impression of a small, Compact bodied bird with a large head.
For ageist I hope for others. But I think the white forehead of an adult female should be visible (any more pictures?), I find it regular surprisingly easy to see, maybe it's such an active bird? and the randomly, sugar cube shaped white spots on the wing should make this a 1cy bird? Or is it just a mount issue? And after consulting
http://blascozumeta.com/specie_files/08870_Dryobates_minor_E.pdf , are the primaries spotted with white or not?
I hope for more comments about ageing. See my other question regarding Great Spotted Woodpecker. Thanks!