Radiator Fan wont stop when car is cold

Hi All

Looking for some advice,

I have an 09 plate skoda octavia which is used as a taxi, its currently done 44500K miles which is still pretty low, but when the car is cold or not used for a week ( I have two jobs) the radiator fan kicks on till the battery is dead.It has happened a few times but the car when running is usually fine which does not overheat etc

So far I have taken it back to the dealer and he has reported that there is an ingress of water in the gear box which is causing the fault, he also stated that I have changed all the fuses ????? (mystery time). He stated that I have driven into a puddle which has caused the seal to break and then he said that I had removed the fuse box cover and this is the case, unfortunately the fault happened before the box lid was removed to allow me to remove the 30 amp fuse which controlled the fan.

I have so far been arguing with SKODA customer service that the fault which is not of my doing and the fuses were not changed by me so this is now an enigma and I am know being faced with with a £300 bill however this is the best part is that I Read here that dampness can enter the ECU and cause the sensor to trip or that the thermostat can be corroded.

I am completely annoyed with SKoda customer service who say I should take it up with the dealer and the dealer said I should take it up with them so I need help

1. If the fan comes on how can this happen.

2. Why would ingress of water in the fuse box cause the radiator fan to come on.

3. Why would the dealer or the previous owner (europa car) Change all the fuses in the engine compartment