I found Mobile Unlocked via Giff Gaff. They were well rated and offered the lowest price for the code that I needed for my HTC DesireS. The order process was quick and easy and the response email with the code and instructions came back well within the time that was quoted. The code itself worked first time and dispelled all my doubts about purchasing a service like this without talking face to face about it with anyone first.
An all round excellent service!