ok at the bottom you will see a line that says logical volume and a large number ending in 2c09
copy the large number then type in "diskutil cs delete volume largenumberhere" and put a space and paste in the number you copied earlier in place of "largenumberhere"
Cheers again, I've just left for work and will try it when I get home. Watch this space!
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Who cares if not apple will fix it. Stop wasting time and your sanity and just go to apple and say its broke and let them deal with the headache. Probably something is wrong with the hard drive in which case apple will need to fix it since these things are no longer user friendly replaceable.
And wait weeks, prob months? I will but only after I've exhausted all other avenues!