How long is your wife's sabbatical or perhaps that question should be how long do you contemplate that the LC will be in Spain?
Vehicles brought to Spain can run on their registered country's registration plate for 6months. They must have a valid road worthiness test certificate (UK - MOT/Spain - ITV).
Was the model sold in Spain/Europe?
Over six months they need to be registered with the Spanish authorities.
Assuming you have owned the vehicle for over a year prior to importation, this shouldn't take or cost too much, however if you have altered the seating, added extras to the original specification then those will undoubtedly have to be removed for the matriculation test and certification. Being under 30 years old they may want to charge you import duty on its value according to their book. You will do well to get it registered here for under 1250 euros and when you take it back, there's no refund and you would have to de-register it for export.
But you could consider bringing it in on a 'Carnet' which, if memory serves lasts for a year and is renewable. This has added value because if the lights a not 'E' marked they will all have to be changed and a Carnet is around 350 euros a year.
Where in Spain will you be based? The rules, although in principle are the same State to State, but they do vary.
The process can take some time but they give the owner a document to say that you have started the process, meaning that you can drive the vehicle.
If you have further questions, just ask, or pm me.
Regards,
Rodger