On 27/10/2020 14:57:12, me wrote:
I'd like to wire the shower room extractor fan from the shower
pull-switch so that it goes on with the shower and not the light. I
found some info where one person said it's a no-no under current
wiring regs but could be done via a contactor, and another says it
can be done without a contactor as long as it goes via a fused spur
from the shower switch.

Any electricians here can tell me which is the legal way to do it as
I'd like to do it through a fused spur from the shower pull switch
for simplicity.

Have you considered of a PIR sensor to detect someone in the bathroom?
Might be additionally useful for when someone does a smelly No 2.