MK1 focus 1.6 coolant temp issue

Hi everyone, new to the forum but been having a gander at the site for a while. Hoping some people on here with experience could help me out.

I have a 2001 focus 1.6 petrol, I think engine code FYDB but not 100% sure. Had it for about 2 years now and had no real issues with it. Have not had any work done to the cooling system in the time I've had it.

Recently noticed that the radiator cooling fan occasionally starts running whilst I'm driving along at a steady speed 50-70mph. I can tell because the headlights flicker as the fan cuts in and I can hear the fan running if I come to stop after crusing. Everything else to do with the cooling system works fine, heater blows hot, temp gauge on dash has never risen above halfway, no loss of coolant (only topped up a tiny bit a couple of times in 2 years). 

Like I said I've not had any work done to the cooling system in the time I've had the car except check the antifreeze strength which was ok. Only noticed the fan issue recently and especially seeing as though it's winter I would not expect the fan to need to come on whilst driving. I know that the fans come on with A/C on and that A/C comes on automatically when the windscreen is selected on the heater dial. I've made sure that heater and AC is definitely all turned off and it still does it. 

I've also used the function on the instrument cluster which displays coolant temp and whilst driving the temperature normally sits between 99 - 103 degrees and occasionally up to 104 which is when the fan cuts in. This seems to high to me and I would suspect that the coolant temp should remain in the range that the thermostat opens and closes. 

To complicate things even more ive checked coolant temp with a snap on scanner and the readings do not match up with instrument cluster readings. Sometimes scanner reading up to 117 degrees. 

As far as I can see my engine only has one temperature sensor on the top of the head (CHT sensor)  so baffled where this other reading had come from. 

I've looked through plenty of online forums about foci overheating issues but nothing like this. Main thing i want to find out is why the coolant temp readings are different. It seems the zetec engine uses a strange cooling system set up. 

Anyway, apologies for long post but trying to provide plenty of info. Thanks in advance