Oxford & Cambridge love standardized testing, which you seem to be very strong in, but neither of them offer business at the undergraduate level.
Quick facts:
=you can only apply to either Oxford OR Cambridge;
=you apply to study a specific subject (usually one, but occasionally a joint honors, ie, History or History + Modern Languages);
=for many courses you have to submit graded school work and/or sit a specific aptitude test (before interview for Oxford, at interview for Cambridge);
=the application deadline for both is 15 October; registration deadline for Oxford aptitude tests is the same day and the tests are on 4 November this year.
=your application essay (Personal Statement) demonstrates your interest in, and aptitude for, the subject you are applying to study, including how that interest has been expressed outside the classroom
=the numbers, recs, PS, written work & any aptitude tests are used to make the shortlist for interviews.
=the interviews are not get-to-know-you, American-style, but more like a cross between an oral exam and a lesson, designed for the tutors to see how you think, how you process new information, how you handle the tutorial format, etc.
=Oxford interviews in person or by Skype; Cambridge only in person