Qasim999,
I'm guessing from your UCAS points that you didnt get into a very good university for Econ? That 99.9% rules out trading for a bank. You could trade for an arcade like futex since they are more concerned about drive and motivation for trading, rather than academic qualifications. As for Tibra...their selection is extremely tough. Their business model appears to revolve around only taking on the brightest of people (filtered out through an extremely difficult test with a very low pass rate). Again, sorry to judge; but the only indicator I have is your UCAS score and on that basis, I doubt you would do well. Ask yourself the following questions...
Why do I want to be a trader?
Why would I be good at being a trader?
What makes a good trader?
The above comments aside, If you really want to be a trader - go for it. Buy yourself a copy of Hull and read it cover to cover.
And remember....Being a trader is less about fast cars, model girlfriends and cocaine and more about 5.30am wake-up calls, hard work, study and more hard work. Good luck.