Its only 18 months old and didn't extend warranty so not what I hoped to hear but thanks for the reply.
Excellent take it to apple point out that it must be a manufacturing defect and calmly and firmly insist they fix it, don't take no for an answer and print out apples own blurb from the website about 6 years limited warranty from their website. They hate it but they can't argue that anything you did caused this.
Here is a link to your legal rights as apple themselves see them.
http://www.apple.com/uk/legal/statutory-warranty/