Insuring an EU Registered Car in Spain
If your car spends over six months of the year in an EU country other than Spain it is necessary to take out a European insurance policy with the home insurer. EU regulations mean that all vehicles must be insured in the country in which they are registered. Therefore if the car is (for example) UK-registered it cannot be insured with a Spanish company. The vehicle can, however, be insured with a British insurer in Spain, by using the Spanish branch of a UK insurance company.
As the law stands a foreign registered car can spend six months per calendar year on Spanish roads without any additional paperwork. It can remain in Spain indefinitely as long as it is garaged on private land (not left on the roadside) for six months per year. The vehicle will need to maintain a valid roadworthiness (MOT in the UK).
You are no longer able to insure UK registered cars in Spain and will have to change the registration of the car to Spanish plates if you intend to keep the car there for any length of time.
Direct Line has set up their Spanish Car Insurance operation with the huge community of English Expats in mind. They provide your policy in English and all the support staff are fluent in at least English and Spanish.