Oh okay - I don't think they're even facilitating 4G yet. I tried them but wasn't impressed and found them to offer poor signal here in Cardiff vs 3. Now that they only offer unlimited data on 18 pound goodybag even less of a reason to go with them, personally. With 4g around my college I often stream YouTube videos in 720p to my phone and can reach 10GB in a month no problem.
Not to be off topic though, what's the OPO like to hold in the hand, and how's battery life? I find its a bit slacking on my Z1.