Both are poor choices. If you have a 2:1 in Biomedicine, I don't see why you shouldn't apply for decent universities for Finance, or even top ones. How is your 2:1 in terms of percentage? If it's a low 2:1, you're going to find it very hard to get into a top university for finance, but you may be able to get an offer from at least a decent one.
By top university, I'm referring to Oxbridge, Imperial, LSE, UCL, Warwick, LBS and CASS (after Oxbridge and LSE, in no particular harder). By decent university I mean Durham, Bristol, Bath, Manchester, Edinburgh, St. Andrews, LSBF etc.
An MSc in Organizational Psychology at a top university is a waste of money if you want to go into IB. Just as an MSc in Finance at a university as low perceived as LJMU is.