I think of immigrants as people of working age who need to work say in Spain.
I tend to think of expats as people who have an income before going to say Spain.
However I have seen the documentaries on Sky with Brits running bars and cafes for a lot of years and out of season overseas or managing properties for Brits (if they have learnt Spanish etc).
A friend of mine has taken out French Citizenship and he is 100% English and lives in London, but his wife is French and after BREXIT vote they were worried about her ability to stay in the UK long term. He had to learn French and pass verbal and written tests in French.
I can see the attraction of the climate. especially in the summer months in Spain and the south of France, but it would be not enough for me to leave the UK, second home maybe but not main home.