I'm a Brit who spends a fair amount of time in the USA during the year; I'm in NYC for a month now. If I buy an unlocked iPhone 5s here, will it work on any of the UK 4G networks when I'm back there? The GSM will work fine, not worried about that. But the data concerns me. My UK bought, unlocked iPhone 4 works here great; especially as t-mobile in NYC now have updated their 3G network - but a long time I could only get Edge. Anyone know?