"Trevor Smith" wrote
| I am fitting an 4" extractor fan in the bathroom wired from a junction box
| on the lighting circuit so does it still need a double pole isolator
| switch?.

Yes, it needs an isolator for mechanical maintenance.

If you are using a run-on timer you will need a triple-pole fan isolator
switch. You might as well use one anyway, as they have a little fan symbol
on and can be locked off, which is required if they are not 'under the
control' of anyone working on the fan.

Owain