I'd say it's actually lucky you're being interviewed at all! My first job took about 25 applications without ever hearing back from the schools, and two unsuccessful interviews before I stroke lucky. It's still quite early days but you may wish to reconsider the "getting the QTS" bit and investigate whether it's possible to get it on the job, e.g. via the GTP (which some independent schools do participate in). You don't say whether you've got any experience of working in schools, or with young people - these days getting a teaching gig is a little harder, Oxford or not, so you need to prove to the schools that you're in it for the long haul and that they should choose you over someone who has given away a year of their life to gain QTS.