MobileMe + iTunes

Hey guys.

I've signed up for MobileMe several weeks ago, and now I'm facing a problem. I can't change my current iTunes ID into my new MobileMe e-mail address. Though I'm pretty unsatisfied with Apple's weird decision not allowing the change to happen, I tried other solutions such as changing my iTunes ID into a nickname. However, when I went to myinfo.apple.com earlier this week, I found nowhere to change my ID. So, where shall I go now? Is it actually possible to change my ID into a nickname? Anybody has got a solution?

Also, since I'm moving to Britain this September, I've decided to move to iTunes Store UK. Will I have to assign my credit card info to change country? Are iTunes Gift Cards able to make the change?

Thank you!