In reply to James Malloch:
I don't think it will make that much difference....I am doing a BSc in Geology as a mature student amd I am doing an Exploration Geophysics module.
I think if you understand all the maths and physics part of it, you can pick up the geology part of it quite quickly, and am sure the MSc will be even more Maths/ Physics based. I even think my tutor for this course is a mathmetician/ physicist turned 'geologist'
Does the Course-amble tell you what will be involved too? BTW, I think there are other Uni's which do this kind of course too....
I am sure there are people more qualified on this site to advise than me, but I'm sure if you do this, it will open a world (literally) of exciting jobs.
Anyway, good-luck