Using the Insurers is a good idea.You will probably have to show that
Masa have ignored request to deal with the problem. To this end it might be an idea to send (more) emails or faxes - or both- to customer service in Alicante, keeping notes of dates etc.
Everyone may already have these, but just in case, here they are again
Masa service 0034 965 142 149 .
contact Susana Guerra (Speaks English)
Fax 965 204473.
There is someone living on SG (can't recall who it is at the moment) who is a friend of one of the Directors of Masa. If he is reading this, perhaps he could have a word.