As noted above you can get Vodafone to unlock it for you although this is generally the more expensive way to go. If your down your local high road or near a market or better still are in London then the cheapest solution is to pop into one of those dodgy electronics shops and have a bloke do it for you there and then. Takes only a few seconds literally once he has cabled it up. No need to send off the phone or anything like that although there are those options as well.