I will say you may still have a chance with IB because I know people who did succeed with MS Finance. IB prefers smart candidates with high scores (like GMAT, GRE, GPA). I got an interview before with a big IB, but kinda blew it because I never expected to get such an opportunity. Therefore, if you really like IB, you may still have a shot.

Meanwhile, as for Corp Fin, it can fall into so many different dept/functions. I will say it is always good for you to have solid background in Accounting/Financial Analysis/Excel/Communication Skills. Most of the time, you will start with a position that may involve month end closing, reporting and analysis as entry level employees.