It's a shame that some Spanish insurance companies act this way. It's like they get their teeth into you and won't let go. We had this with our bank insurance and it was so difficult sorting it out that we had to leave it another year and then start the process 4 months in advance the next year with a letter by snail-mail which they insisted on and then I insisted on confirmation by email thatthey had received it and only then could I start the new insurance.
In the UK I compare every insurance I have each year and right up to the renewal date I can change companies. How dare these companies act this way...there really is no need other than money grabbing.
I must say I have heard that some insurance companies in Spain have changed now and do not insist on the notice period so it's definitely worth asking about any notice period and getting it in writing that there isn't any.
In the end I went with a UK based insurer for our holiday home in Spain and treat it just like my UK insurances and compare prices each year knowing it can be switched right up to the renewal date.
Jan