Ok so here's another guide. Not saying the other is rubbish but this could be a good alternative.
Step 1. Patience is the key. Wait until November the 9th and get yourself a tasty new iPhone, preferrably from an Apple store. The idea is you take it home and activate the contract by itunes.
Step 2: Do not activate the contract. Instead, use many unlocking methods to set the iPhone free. Sure, they may of updated the firmware, but they'll be a new app around the block by that time.
Step 3: Do you have a contract? Well, if not, do this. Find yourself a contract that gives you a good data plan, and a good handset, and use this for your iPhone. You then have a handset to sell on eBay and recoup costs, (nokia n95 e.g., could almost get the price of the iPhone back, effictively making it free).
Step 4: Use the sim from your new contract in your iPhone, and enjoy! Remember, you'll get no visual voicemail and no unlimited data (unless your new contract plan includes it), as per the other guide. Although, the Cloud Wifi network may work, who knows. It's not like it can validate through phone number as it doesn't work that. It might sense once you're using an iPhone, it gives you access, but I could be totally wrong with that.
Benefits: No faffing around sending money to people you don't know in the US. No customs. You get a full UK warranty, just return it to the apple store if it goes kaput. UK charger and accessories.
Just thought. You could even find a contract that gives you cashback, there's always some roaming around where the you get cashback to the equivalent of the contract - making it free. You'd have to pay for the iPhone, but you'd be getting contract minutes and texts for nothing!