Should I apply to Oxford to do maths with my results?

Originally if i was going to apply to either oxford or cambridge, it would have been cambridge, however I was told that Oxford look more at your GCSE's and don't look at your ums. I got AAAB at AS level with maths,physics,geography and chemistry. My UMS wasn't high for any of these apart from geography. I dropped geography and picked up AS further maths since the option was available to me so I am now doing chemistry maths and physics as my 3 a levels. In my GCSE's I got 8A*'s and 2A's and am unsure if it is worth using an application slot for oxford.

Thanks.