I logged onto my email earlier than usual this morning and was surprised to find an email from O2 stating that the iPhone would be available for online order from 8am. I put my order in at 8.20 and, pending to approval, I'll be getting my iPhone delivered by courier on Friday.
I've just read now that O2's online store has collapsed under the weight of the number of pre-orders and they've posted this:
I must have been one of the lucky ones! I'm amazed they didn't anticpate the volume of orders.