If you want the best chance at Oxford, go for traditional subjects. My brother is currently doing History and Politics at LMH, Oxford. He did Geography, Politics, History and Philosophy at AS Level, dropping the Geog for A Level.
Any of these, plus English Lit., any modern or ancient language, and Theology (RS) would all be superb choices. Maths won't harm the application either, the sciences are perhaps a little irrelevant.
I'd avoid subjects like media studies - they can be still be useful and interesting, but will be of less help when applying than a more traditional one. Hope this helps!