Where and how can I purchase an extension to a SLT-A55's current 1 year warranty in the UK?

Currently considering to purchase the camera, but before I do so, would like to know the options available to me on extending warranty. I know I can buy an extra 2 years of warranty at John Lewis, but what if I want to buy it from a different retailer who doesn't offer this? Can I buy it from Sony direct post purchase of camera?