Welcome mate and what a great write up and introduction.
I hope the Terrano looks after you, they are such great vehicles and we have the best wealth of knowledge on this forum in the UK, if not the world
As for the extra gadgets, like Elty said, you're going to need to just trace the wires back. As you're in a cold country, could it be an electric engine pre heater such as a Kenlowe HotStart etc ?
Looking forward to seeing and hearing more