The iPhone will launch throughout the UK on 9 November, just in time for the holidays.
O2 also announced at the event at Apple's flagship store on Regent Street in London that it has partnered with Carphone Warehouse to offer the handset at over 1,300 retail outlets.
Apple will ship only the 8GB version of the iPhone in the UK, which will cost £269 including VAT with a choice of three 18-month contracts costing £35, £45 or £55 a month.
All contracts will provide unlimited data within O2's fair usage policies, and the various plans will offer different levels of inclusive texts and voice call minutes.
"US iPhone customer satisfaction is off the charts, and we cannot wait to let UK customers get their hands on it and learn what they think of it," said Apple chief executive Steve Jobs at the London event.
Customers in the UK will have to activate the iPhone through iTunes on their PC or Mac. After purchasing the phone and connecting to iTunes, users can select a tariff, undertake a credit check and activate the phone.
O2 has also sealed a deal with wireless internet provider The Cloud to allow iPhone users seamlessly to access the internet over Wi-Fi at any of the company's 7,500 hotspots throughout the UK at no extra charge.
A similar deal exists in the US with the Starbucks coffee chain, but there was no confirmation that the deal may be expanded to the UK or Europe.
O2 chief executive Matthew Key said at the event that the operator will provide dedicated staff in every retail store, and allocate 1,000 customer care staff specifically to help users with the iPhone.
Jobs likened the partnership with O2 to dating and marriage. "Partnerships are a lot of work and, like marriage, you want to go on a few dates before you pick a partner," he said.
"We believe we have picked the best partner for us, but there are a few upset girlfriends around."
Neither executive would discuss the details of the revenue sharing model between the two companies, but Jobs did say that "conceptually it could work both ways".
This could allow O2 to gain some of the revenue generated by Apple from the sale of content to the iPhone.
Jobs also refused to comment on further rollouts of the iPhone across Europe, saying that he was in London to talk about the UK only. But he did add that further announcements would be forthcoming.
Key revealed that O2 will offering a flat rate data package across all of its contracts from 1 October, moving away from its current pay-as-you-use model.
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