Headington - school isn't aggressively selective with about 140 sitting for 90 places. Head doesn't like overly coached children.
St H&K - have large numbers applying from state and preps for only 60 places, but there are openings at age 9 and 10 so you could try and get in now.
Oxford High - seriously over-subscribed at all age groups. If your daughter has an obvious weakness then its unlikely she'll get in, but there's no harm trying.
I have no kids at these schools, but this info is accurate although there's not much of it!