Any hope for Oxbridge?

I wanted to study economics at Cambridge before I received my results, but I was shocked to find out that I did poorly in my AS-level exams. I got AAAAAB in Maths, Further Maths, Geography, Physics, Japanese, and Economics, with an average of 91.1%.

The disappointment was of course the B in economics, which was a surprise because I was getting 90%+ on all assessments during the school year. I'm getting a remark in the hope it goes up by 5ums to an A (77 unit 1, 78 unit 2).

If my grade does jump to an A, should I apply to Oxford who don't look at UMS, or the university I want to go to in Cambridge, despite the fact that they do look at UMS?

Lastly, should I even try for Oxbridge economics if it doesn't go up to an A? For context, I got 6A* 5A at GCSE and am predicted 2A* 3A at A2-level (same subjects as above but without Geography). I'm trying to persuade my economics teacher to predict me an A* because it is still easily within the realm of possibility.

Thanks.