This is tempting: iPhone Upgrade Programme – Apple (UK)

http://www.apple.com/uk/shop/iphone/iphone-upgrade-program

Getting the latest iPhone has never been easier.

With the iPhone Upgrade Programme, you no longer need to wait for your carrier contract to end to change your phone. After 11 payments, you can get a new iPhone and simply start the programme again with your new choice of model, colour or storage capacity.

From £33.45/month for iPhone 7 32GB