If you really want to be up in the corporate ladder; I would highly recommend getting at least a degree...especially in the banking industry...think of it as just staying competitive against the bunch of kids who are highly qualified coming out of uni...
Although they might not have the 3 years experience edge over you; employers are still gonna prob prefer them over you...since that they have something to prove that they are capable to learn and excel; the degree signifies more than just study, it demonstrates ability to adapt to new things. And face it...most kids who come out of uni might get a graduate program which pays equal if not more than you when they are fresh out.
I have to agree that study is not for everyone...and if you hate it...then there is no point, but career wise, i think uni is essential nowadays...even most managers and CEOs have to go back to study just so that they don't feel outsmarted by their subordinates.
My opinion is...if you want to go into a career straight out of high school, you'd be better off finding an apprenticeship in another industry...If you're really determined in finance and banking...i think...HSBC has a apprenticeship for tellers and stuff too..
whatever you choose, good luck =)