Most first year business courses at Aston follow a similar first year in regards modules, after the first year, it is possible to transfer course where possible. Aston does a great job of attempting to keep students happy in regards their tutoring.
Even if you couldn't change at the start of this year, the course will not be that different from what you'd be doing on BAIR, so I think you wouldnt find AFM year two that inaccessible.
Please note however, that I dont do either of the courses and am working on the understanding they're not overly different in the first year. However, if you ring Aston up and simply explain your situation, theyll be able to offer you a solution im sure. Perhaps ring the business school on +44 (0) 121 204 3030 which is the number for undergraduate course enquiries.