UK retailer Play.com is now offering fully unlocked iPhones that will work on any UK network, but it all comes at a premium price.
The site is currently offering the 8GB iPhone 3G for £550 and the 16GB for £600. That would equal about $801 and $874 according to the current exchange rates, which is a far cry from AT&T's no-commitment phones that cost $599 and $699 respectively, but those are not unlocked from AT&T's network.
Play.com claims that they are able to make the iPhone available unlocked and SIM-free due to, "EU legislation ensuring the sale of sim free mobile phones."
The site currently estimates the phones will ship in 4-5 days. As an added bonus, shipping is free, but that is probably a minor concern to folks willing to fork over that much for an unlocked iPhone in the first place.