Chaging firm and insurance around?

Hi, I was wondering what options are open to someone who has already firmed and insured their university choices over a month ago. I have fimed Durham for Education/English, and I love the university; with English/Art History insured at York. The course I want to do is English/Art History, and I firmed Durham on the basis that I would ask to change courses upon getting results. However, I emailed the deparment and they said this is unlikely - plus, I would need to get A*AA which is a bit of a stretch. Furthermore, I would be applying for the Liberal Arts course (combined arts) as the University doesn't have an as well developed Art History department as York does. I love Durham because of it's college system, but if I can't change courses I don't want to be stuck applying for accomodation at York etc. late. Both courses require AAB. I don't like York University so much but somewhere, something has to be sacrificed, so I wanted to try and change my choices around so I firm York instead. Thoughts? Thanks.