customs paperwork

Hi

Has anybody recently moved to Lanzarote and shipped their belongings in a container ? If so what paperwork do we need for Customs apart from an inventory and our NIE numbers which we have already obtained through our solicitor. Moving in March when we complete the sale of our house and purchase of villa in Playa Blanca. Seem to be getting conflicting advice from shipping / removals companies and cannot get a definitive answer - even from the Spanish Embassy ! Some say we need to register as residents to get certificate required by customs but my solicitor in Lanzarote informs me this cannot be done until we complete purchase on our villa and are living there. Help from anyone on this gratefully received. What paperwork exactly is required to clear our container of household goods through customs procedures ?

Thanks in advance for any help or advice anybody can give on this.

Dodgydj