Thanks to all who have replied. I must admit that I assumed
that a "normal" light switch should not be installed in a
bathroom. Even if this is legit, would it be regarded as
best practice?

I'm worried that it might not get passed by a picky BCO (I'm
replacing the entire bathroom suite so the work is
notifiable).

I'd like to avoid the hassle of chopping thru the ceiling
to gain access to fit a pull-cord switch as it would be
beyond my competence to re-plaster everything afterwards
(trust me on this ;-)

Finally, can anyone advise as to where to obtain an IP
rated switch suitable for indoor use, or am I on a fools
errand looking for one?

Thanks again

--Mike