Hmm, be very very careful there. It may well be OK with a type B MCB
and a PME supply, but if the protective device is a 45A BS 1361 fuse and
the bathroom wiring is pre the bathroom amendment (so 0.4 second
disconnection needed) then you'd need Zs 0.6 ohm. If the service is
TN-S (Ze max. = 0.8 ohm) then you're stuffed unless there's an RCD fitted.

Indeed. By saying I hadn't checked it, I meant that it needed to be checked,
not that you shouldn't bother.

However, I would always RCD an electric shower and it would always be on a
Type B MCB. Not that I would install something that required an RCD to meet
earth loop impedence requirements, though. Even on a TT system, I would
ensure that it would be compliant when the earthing is upgraded.

Christian.