Same story with location on WP7 too. I chose UK as marketplace was not available for Greece but then it didn't accept my credit card as it assumed UK. The other awful thing is that it forces your account location language even if you explicitly set it to english.

As for the video, I just read that VLC are starting a port for RT so you might have some luck there. I also heard about Metro firefox but not sure if that is going to be available on RT.

I hope you can hack it and install plasma active on it