Mobile phone unlocking is a hugely confusing grey area. Is it even fully legal? Unlocking your phone void your warranty? Where should I go to get my phone unlocked? And what about blocked phones?
Fortunately, we just stumbled across this great guide by giffgaff, a popular new sim-only network. If you want to switch to a new network, check out the giffgaff unlockapedia for the complete lowdown of the mobile unlocking.