Not been near or punting for a while now, but AW and Vivastreet have plenty of options. There has long been high numbers of Hungarians and Brazilians working in Stratford, of very variable quality, so do your homework first.
In my experience, some of the better and costlier options suddenly pitch up on AW after booking a hotel for a week there, as in book into hotel and then change AW location. If you're staying in a hotel in or around Westfield then chances are there's a WG staying in there. Could even be the woman you share a lift with!