I need advice on english pronunciation

Hello,
I am studying english and this is my first year at university. I started studying phonetics (sth difficult for me) but the problem is that for six years I have learnt Amercan english and now I have to learn the british accent (RP) and is too difficult! Imagine..I speak spanish (I'm from Argentina)... the advantage (I think) is that I have good pronunciation but British english is different from American english. At the end of this year, I have a final exam,in which I will have to read and talk like an Rp speaker..or close to it. What should I do?

thank you.
Ana.

Are you sure that you have to have a BrE accent and not just a standard AE one?

[FONT="Comic Sans MS"]the only way I think u should practise more at home , listen to news (English accent) and imitate them... then read many books about phonetics.
I'm also a student learning British english, so I know that the way to pronunciate in British accent is more difficult than in American accent. However, I think that when u can speak American English, u'll find out the difference in stress, vowels, consonants easily... Just practise more often, the only way to improve ur Bris accent :-)
Good luck ![/FONT]