Rear air conditioning? anyone else got it?

after buyimg the latest one i have noticed that the very rear left window is smaller and there is a bit of perspex type glass over it also it has a what seems like aircon motor in behind the dicky seat, nothing about it in Haynes manual OR handbook do i need to gas this up aswell? as my normal aircon in engine is currently not working needs a new belt will the rear one work if thats what it is, also i seem to have to press the little button on dash for any air to come through vents in the rear, all very mistifying, any advice gratefully accepted cheers