Ahoy Bernice, I have just used a gestor based in Sevilla to transfer a UK plated bike to Spanish plate. Ask at the marina if they know of a gestor or gestoria more local. Your first challenge is to get a ficha tecnica for the vehicle, which is done at an ITV station but you first need a ficha reducida which in my case was organised by the gestor through the engineering college. There is an ITV station just off the autovia at Huelva and another at Palma del Condado which is the one I used. Very helpful staff there and no waiting lists as there are in Sevilla at the moment.

That was very helpful, thank you.