I'm not sure what happened, or how to fix this, but a random box showed on my iPhone saying "iPhone Activated". I pressed the only option available, "Ok", and didn't think anything of it. I realised a while afterwards, that I'm suddenly on the US App Store. It has all the prices in dollars, and some apps that are not available in the UK store. I can download apps that are also in the UK Store and it won't let me download any US-only apps, but it's weird that this has happened. I've tried hard reboots, etc, but no joy. It also affects the mobile iTunes Music Store as well. My account on my PC's iTunes is still UK. I have all the normal service from O2(EDGE, 3G, ect).