Thanks, El Presidente. I have unlocked a phone before and it's because I know that it was easy to do, it makes me wonder why CEX sell the Vodafone version of the phone much cheaper (even the A grade is cheaper that the B grade from other networks). Surely, once you unlock phones from different networks they are all unlocked so are just the same as each other? For that matter, why don't CEX unlock all their phones and sell them as unlocked which they charge more for?
In order to unlock the phone I'm looking at, I would have to buy it from CEX first and I don't wan't to risk there being some reason I can't unlock it.