I'm currently trading in GBP on gox (i'm from UK) however I'm being charged 2.5% on every trade (on top of the 0.6% fee). Is there someway I can change my GBP to USD in my wallet, so that when I trde I'm getting better rates....

Hopwfully I can then in turn convert the USD balance back into GBP before withdrawing it again (I intend to make lots of trades in a week, but just make a withdrawal once a month).