A quad a Scooter a Moto or a Trike all require registering, your neighbours 3 wheel truck is probably a Piaggio Ape, Quads are seriously stupid money in Spain about twice the price of buying a second hand one in the UK!! if you are trekking over on a regular basis till you retire you are probably better off driving here in your UK registered car as you probably wont't stay for more than 6 months at a time!!