Spain hasn't ratified the Vienna Convention.On the basis of the "Vienna Convention on Road Traffic", the vehicle's equipment has to run in accordance with the regulations of the country of registration, not the country in which it resides.
So if your country and the country you are going to have a convention, then equip your vehicle as required at your home country.
There is a tourist mode (tourist light) which detects driving on the other side accordingly and adjusts the beam pattern. The manual does say for long stays abroad you should get your headlights changedIf like the Ateca which they will be they have a legal spill of front light on LHD roads, only if you take up residence do you need to get your headlights changed. No sticky deflectors these days.
Ah ha. New tech perhaps. 2016 LEDs they just legally spill light but built into the hardware nothing clever about detecting whether you were driving on the left or right and switching modes unless it was one of those Seat publication errors.There is a tourist mode (tourist light) which detects driving on the other side accordingly and adjusts the beam pattern. The manual does say for long stays abroad you should get your headlights changed