On Wednesday, UK wireless carrier announced that it will open its retail locations at 7 AM on July 11th to begin selling Apple's new iPhone 3G handset.

The company offered a warning to customers, who were also informed that the retailer would only be prepared to sell one unit to each customer during the launch.

"Orders will be placed on a first come first served basis," O2 warned, "we will be writing to you again before the 11th with details about how you can place your order."

According to Macworld UK, O2 is offering the iPhone 3G to existing iPhone customers prior to the end of their existing contract, but conditional on the customer taking up a new 18-month contract.

The upgrade deal will be available between July 11th and October 11th wherein the 8GB iPhone 3G will be free to existing customers on the £45/month and £75/month iPhone plans and £99 on the £35/month or new £30/month plans.

If you're on the other side of the pond and have heard anything interesting about this, let us know in the comments or forums.