Thanks for all the replies.
The important point for me was that the fan is switched on automatically depending on the humidity level as I can't rely on the light being switched on.
If some fans will not be strong enough, are there particular manufacturers to look at (or avoid) ?
I want to put an extractor fan in a bathroom that has bad condensation.
There is a window in the room, so I can't rely on the light switch to operate the fan.
If a humidistat fan was connected directly to the lighting circuit so that power was always available to the fan, would that work?
I...