Chemistry or Chemical Engineering?

Hi everyone. I have this little problem with my application and am really unsure of what to do now.I have received an unconditional from Edinburgh University to study Chemistry but now wish to Chemical Engineering instead. I had contacted the university and they said that they would have transfered me had they had any more places for Chemical Engineering. They have now said to call back on the August 16 as that is when the first "clearing" day happens for University. There is no guarantee that there will be a place then but they said if even one seat openz up they will give me it. This means that i would need to defer my Chemistry offer until 2017. If I don't get a place on August, I would need to take a Gap year.Any advice would be greatly appreciated as to what to do.