Far from jumping down your throat, I think this has the potential to be a fascinating mystery. It's a given that most hill figures (certainly the white horses of Wiltshire) are not prehistoric - many are relatively recent. The exception being the Uffington White Horse, which as you pointed out may well have looked quite different to how it looks today.

I think the Foxhill image, which may well have existed as a land figure, may be medieval. I've been looking at illustrations of medieval rural life and there are similarities in the clothes.
http://www.bl.uk/learning/histcitizen/medieval/rural/rurallife.html

Also, the owl was not necessarily a good omen in the Middle Ages, the opposite in fact.
http://bestiary.ca/beasts/beast245.htm

Could be this image was a depiction of something rather more unpleasant than our current folk-lore inclinations suggest.