A friend has a new flat. The bathroom light is reachable by anyone
standing in the bath, and the bath has a combi-boiler-fed shower over
it, so there'll be soon be lots of water and steam in the vicinity.
(Before that, there was a weaker elctric shower in the same place.)

As soon as I saw it I said I thought the bathroom light was a problem,
being a 'trendy' cluster of 3 spotlights, maybe ok in a bedroom but not
there. I've not checked yet, but I'm near certain that it's a 240V
fitting, not a low voltage one, mainly because I've not seen any
transformer anywhere.

The light is in Zone 1, possibly borderline Zone 2, but I guess not.
When I looked at bathroom lights in B&Q, even those marked as suitable
for Zone 1 said on their instructions (buried inside the box, of course
- good thing I opened it for a read) that the circuit should have a RCD
fitted as well. The house does have circuit breakers rather than
old-fashioned fusewire fuses, but I'm not sure if the breakers are
modern enough for a RCD-type to replace the current lighting circuit
breaker.

I'm sure that's what's required in the long term, but I'm wondering if
there are any short-term alternatives. I presume that even an enclosed
Zone 1 type light would be better than what's installed now? I also
wondered if one of the bulkhead-type outside lights would be a safer
alternative?

I also wonder if anyone makes a standalone RCD that could be sited
outside the bathroom (eg high up on the hall wall?) and have the
existing bathroom light circuit routed through it - ie could I take
cable out of the current bathroom ceiling pull-switch and through the
wall to a RCD then back in to the existing light circuit (or something)?

No-one wants to have to dig the existing ceiling apart looking for the
cables in it at this stage, as I suspect would be necessary if we
wanted either to replace the existing lighting circuit just in that
room, or indeed if we needed to completely disconnect that room's
lighting circuit and run a new one.

--
Jeremy C B Nicoll - my opinions are my own.