Water and Electrics CAUTION So I am been....  
Bathroom Extractor fan inop been like this for some weeks...
Outside the bathroom we have the fuse box for the extractor fan.
Inside the bathroom we have a small box with a  moisture sensor and a pullcord with a lit Neon light when the cord is pulled.
On the wall (gable end) we have the extractor fan which receives power when the pullcord on the sensor is pulled, another lit neon light on the fan housing shows this.
I have just been into the bathroom where its bone dry in there at the moment. On pulling the cord I noticed both Red Neon lights glowing then fading out within 2 seconds. Recently when the bathroom is full of moisture from the bath or shower these two neon lights illuminate  with no fan movement what so ever. My question to you experts what do I do next. Electricaly I am competent to sort this problem out what I want to know is, I belive power is reaching the extractor fan the neon light confirms this, could it be worn bushes on the motor or a fault within the moisture sensor where the pull cord is? Please see the images I have posted for the type of fan and circuit in question.
If the fan needs replacing can I remove the fan from inside the bathroom or do I need to go outside climb a ladder then remove the fan unit from the outside?
Thank you.
Keith.....

is that the 12v version when he says fuseox ouitside bathroom

If the tiler was lazy, and did not bring the fan in front of the tiles, then your only option is to break the cover off and replace the fan.  I would then go for a like for like to ensure it covers the scar as best as it can.  Use a few washers behind the fixing screws to bring the new fan level with the front of the tiles, and then perhaps a quick bead of silicone around it to cover any edges of grout.

Can you take a photo of the unit outside the bathroom?  If it is a SELV type, you could test from there.

Perhaps the older humidistats had the neon operating when automatically switched.  I know for sure the newer ones don't (only when manually operated), otherwise you get confused as to if the manual is on or off.