End o2 contract early

I know o2 still haven't decided on what they are going to do about non-iPhone contract customers to upgrade to an iPhone 3g contract. I know in the past it has costs £219 to upgrade (if they joined after a certain date). I joined a few days after the first iPhone was announced on o2 and want to upgrade to the new one now. I have 10 months left on my contract and I know too upgrade on a normal phone early you would have to buy yourself out of the rest of the contract and I am happy to do so with the iPhone, I would even more happy if I didn't have to but if that's the way its got to be then that's that but I really want to know is how do I cancel my contract before upgrading to the new iPhone one. Would it be done in store or would I have to cancel it before by phone or what. And I would want to get it on launch day so I need to know if I can do it before hand and then get the pac code to transfer it instore.