I think a UK school would ask: what can this person add in the classroom or to recruiters? The central bank experience doesn't add much in the classroom, I think, since you sound like you are doing IT ranking rather than managing monetary policy. Neither plan A nor Plan B really require an MBA from a top school. A specialised masters in fintech from Brandeis, SMU, Strathclyde, or Warwick sounds like a better fit.

In regards to your Plan B: although financial firms recruit MBAs in droves, they don't often look at this recruiting avenue for software development. They want MBAs as associates. You'd probably have as much luck landing a job like this without an MBA, to be honesty.

In terms of your Plan A, what kind of role were you thinking of aiming for in the FinTech industry?

You could also have a Plan C: if your background is indeed in strategy and consulting, and you're aiming for a top MBA, you could go the traditional route and try to land an associate-level position in a financial services firm or consulting firm.