Ok that could be one of 4 things....
1. the two 10amp fuses - unlikely but not impossible both have blown but simple to check.
2. the relay E4 (top row, second from right) feeds the high/low steering wheel stalk.
3. oh dear!, the slide main sidelights / headlight switch is a well known weak spot! Can be hard to find one.
4. the high/low steering wheel stalk switch.
All carry the current for the dipped beam headlights and Fiat (in common with most auto manufacturers)
love to cost down every component in the name of profit and these switches are just prone to burning out.
The circuit feed for your headlights comes from the Ign switch I think on a black wire and this feeds 12v to
the slide lighting switch, it too has been known to get fed up with life!
If you can download a wiring diagram and trace power through with a voltmeter, it should get you sorted.
At least the X1/9 doesn't suffer from too many CANbusses!! Better hurry, the nights are drawing in.