How To Separate Bathroom Fan And Light Switch

Hi Guys,
My sister is having her bathroom done and tells me she wants an extractor fan with timer, but doesn't want it connected to the light. She wants two separate switches outside the bathroom, one to operate the light and the other for the fan. The bathroom has an opening window btw.

She wants to know if lighting regs permit this or not? before the electrician arrives.

Many thanks.
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She can have whatever she likes
Is she going to be making the switch outside the bathroom a trigger for the fan, with a separate fan isolator.
If not just use a fan without a timer.
Thanks guys.
Yes Deleted member 11267. If i understand it correctly, the fan will have a isolator or a fcu.
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Converted a bathroom into 2 shower rooms for an elderly couple a short while back, one of which became an ensuite via a knock through from the bedroom. They wanted the extractors operated independently of the lights as they wanted the ensuite (especially) light to stay on at night, so didn't want the fans running. Fitted pull cords in the bathroom next to the shower to operate each fan, but each switch had a neon indicator in so it was obvious that the in-line fans ( in the loft) were 'off' or 'on'.
Isolators for fans were fitted next to the fans in the loft.
HI guys and thank you for all your replies, really appreciated.
I was thinking on the fan wiring today ,and from the little i know, i made up this diagram to better understand what the electrician will have to do. Am i right? She (sister) wants the timer fan to be controlled by a wall switch independent of the room light. In the past I have found that it helps to know a little in advance to understand what a tradesman is proposing to do. (yes the earthing isn't showing in diagram) Many thanks once again.
That will be fine - just put a sleeve Blue L1 to JB wire.
In this config, the fan will come on when the switch is turned on and remain on until the overrun period on the fan has ended following the switch being turned off.
That is the way I said in my first post.
Depending on how long she uses the bathroom, you could adjust the timer accordingly and fit a retractive switch.
Building regs require over run timer, discuss. doesnt matter about weve got an opening window.
Can i nip in and ask something?
I am thinking of putting in a sep switch for the inline bathroom fan.

Now, it is currently worked off of light switch outside bathroom. Would it be easy to buy a double switch as a replacement for the single light switch and use one for the light and one for the fan? Is it just a matter of moving the right wires over to the other switch? Wall is hollow behind switch.

Nephew is an electrician and in the past he said he would sort it. Dont want to bother him at the mo. Just want info thats all. Ta
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Piece of cake if it's a stud wall
like i said needs an overum timer to clear moisture , smells ect. manually switching does nt do this. weve been putting them in like this for years.
Unlikely ...
The SL feed to the fan can be wired from many different places: switch, JB, rose, light ... Your nephew will nee dto understand how it is wired before it can be changed over.
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It's just a cause of pulling in another cable Kool...which is a piece of cake for a competent sparky
Thanks. Nephew will do that then. But changing that single switch into a double is ok then?
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Cheers. Got to find a quiet but good inline fan now
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http://www.superlecdirect.com/venti...nta-inline-2-speed-fan-timed-version-9041086/
Fitted quite a few of these this year.
Can't fault them for the money. One of my sparkys was also very impressed by them and has started using them too. Well made, quiet and an excellent price...