Still? It's my first post.You still seem to be confused between isolators and switches.
I know the difference, I possibly haven't explained clearly. We have four extractor fans:
Bathroom is both controlled and isolated with an isolator switch only. No timer. Can be turned on without the light.
Ensuite is triggered by a conventional lightswitch common to the light. It features an overrun timer. It can also be isolated with a separate isolator switch and light will still work.
Utility Room has no isolator switch. It doesn't work but appears to be controlled by a conventional lightswitch independent of the utility light.
WC has no isolator switch. Is triggered by a conventional lightswitch common to the light. It features an overrun timer.
Hopefully that explains better.