That would have been even better and just goes to show i should have asked first. I made a decision to ignore the electrical regs and put the switch in - it can be taken out of circuit in future and there's a fused spur outside the shower room.
Talking to our electrician the UK regs now seem so over the top as to be laughable - as i understand it you cant even have a ring main running THROUGH a bathroom so each of the electrical devices in a bathroom now needs to have a fused spur outside the room with only the load wire running to the appliance.
I was in Switzerland recently. It's a pretty tightly regulated society with very high construction standards and while we were there we visited some friends in a stunning high-spec 'executive' apartment in Zurich. The fuse box for the apartment was in the shower room wall with a metal door and the lightswitch was inside the room. I dont think the bathroom light switches had an integrated socket (most of the others did) but i'm sure there were a couple of sockets in the bathroom anyway.
In the UK I can have a plug socket as close as i want to the sink in the kitchen where i'm washing up but cant have a light switch in the same room as a toilet? If you're stupid enough to dry your hair in the bath you're probably stupid enough to run an extension lead from the next room to do it.