OP
Why don't you measure the ceiling height and determine whether or not they are zone 2?
i would have thought the height in my case is not the worry. As already mentioned the air gap between the top of the cubicle and the ceiling is approx. 350mm, as if this may trap more moisture within etc than a cubicle of a great distance to the ceiling being able to vent better.
So I take it the min. requirement would be IP65 whether its fire rated or not for best