http://www.allupandon...ng-zones-diagram.html
Only SELV (separated extra low voltage)(12v with transformer) allowed in zones 0,1, and 2.
Outside zones (used to be called zone 3) 230v allowed.
Outside the zones, you could fit a sodding great industrial Ventaxia that would take your wig off ................. if you wanted to ;o)
I'll bet he's worrying about current load. Shower fans are often fed from the lighting circuit. A big fan might have to be fed from its own supply, or from a spur off the ring main (sockets) circuit.
I'm off to check capacities ........... back later.