Answer:
To be an investment banker you have to have an MBA, and to get recruited or really even looked at it has to be at a top business school.
It would be better to take a management degree or to degree in financial sector that might help you in getting a job as investment banker.
You need to go to a top business school to get recruited by the best ibanks. Economics and finance are the best choice of major, then move on to get your MBA. It is really hard to get in without connections.
There are no stated requirements, usually a high level of proficiency in English is required as well as good statistical and analytical skills therefore I would say the best A levels to do are English language, English literature or a combination of the both and Maths, Chemistry, Physics
There are many tasks of the investment banker, but the main goal is to invest a very large amount of someone elses money, plain and simple. The job holds very long hours, forget about family while your in the field.