Hi Daniel
Best thing you can do at the moment is study for your A levels go to university and study economics. This will give you an in at the investment banks (this is what you should be aiming for). Read lots, start with the basics, and ask lost of questions.
Signing up for a board like this is good start, I am sure people will not mind you asking questions.
There is an article here:
How to Become a Stockbroker in the UK that may help.
Chance your arm at getting an unpaid summer job at an investment bank or broker. Employers in our industry are constantly looking for people who have the gumption to go after what they want and although many will turn you down, if you are persistant you will get somewhere.
This can be very important as this business is, actually, a very small community and the sooner you start making contacts the better for your long term career.
I know it sounds boring but spending the next five years studying hard and working for your goal will be the best move you could make.
Good luck!