Lobster wrote:
PoP wrote in message . ..

The fan should be a spur from the upstairs ring main, not the lighting
circuit. And upstairs ring mains tend to come up from the floor rather
than down from the loft. Note the word "tend", you can't count on it.

Why not from the lighting circuit? Isn't that the way to wire them if

Because Murphy's says that if it is going to fail it will do so at
night

you want them to switch on automatically with the light switch (eg as
in the case of an internal bathroom/toilet)?

In this case the fan has two live connectors. One to power the fan
and electronics and one connected to the switched live feeding the
lamp(s).