Investment banks are highly unlikely to give you full credit for your 3 years work. More likely you’ll get credit for 1 year and if you are lucky 2 years. Investment banks are still going to see the 2:2 on your CV and until you have either another strong qualification or some tangible experience to negate this, it is going to be tough to get in at all. You might be better off staying in your current job for a couple more years until you can really sell yourself as an expert in something. Try to approach business people rather than the HR department (or write a stellar cover letter) as otherwise HR could just immediately screen you out because of the 2:2. The job market outside the UK is also going through difficulties now. Do you speak a useful language? Have you worked in an industry or project that has relevance? If so, you could be able to sell yourself that way outside of the UK and get more credit for the work you have already done.