iPhone Upgrades
Networks are currently offering consumers the opportunity to upgrade early, provided they sign up to a new long-term contract.
Orange allows existing customers to upgrade up to 90 days before the end of their current deal, provided they sign up to a new contract.
Vodafone allow existing customers the chance to upgrade to an iPhone 4, with no specific deals to do so early at present.
O2 is flexible regarding upgrades, offering stock of the iPhone 4 to existing customers as a priority.
Even if there is a long duration left on your contract, there is scope for customers looking to upgrade early to the iPhone 4.
O2 enables existing customers to pay as reduced one-off charge as part of their early upgrade offer, the amount varying according to the duration left on your contract.
Consult O2's Upgrade Calculator to see how much you would need to pay to bring forward your renewal date. Note that this cost is separate from the cost of an iPhone deal, and is only available on the condition that you sign up for a new O2 contract.
Vodafone does not currently offer an early upgrade deal to their customers.
Orange permits the addition of an iPhone to your existing account at any point, consolidating the two into one bill that you would have to pay for the duration of the overlap.
Both are pricey solutions to the problem of being tied to a contract, but do enable you to upgrade to the iPhone 4 ahead of schedule.