You could check whether any courses you want to do were in clearing this year- that might give you an idea of whether they might be in clearing this year. Or if you are interested in the Oxford course then you can always take a gap year and apply next year that way you could also tailor you personal statement to both physics and philosophy (or whatever joint degree you want to do). Or accept the physics offer (since you say you are really interested in physics) and join different societies for the other subjects you are interested in. Also, I forgot to say this in my first reply but don't be scared about not being good enough- you've got the offer because that university does want you and they see the potential in you! I am not too sure but I think a masters in one of them should be possible- but I'll let someone else clarify that for you.