MacBook will only work when plugged in to charge

I bought my Black MacBook about a month and a half ago from John Lewis, England, is anyone else had a problem with this model from John Lewis?

There is a black cross accross my battery symbol, my MB works fine when AC is plugged in but as soon as it is removed my MB switches off. When I hold click on the battery symbol it says "No batteries avaliable"
the light on the charger stays green and don't turn amber.
I have tried removing the battery, all the resets reccommended and just left MB off whilst plugged into charge for 12hours but nothing.

Any help would be appreciated, before I send it away to be repaired and without it for atleast a week.

Thank You