There are several expat groups on Facebook, by which I mean, they call themselves that. 'Expats in Spain' might be one. Seek them out, they can have useful posts sometimes.
I am in no doubt that these sites, with many others, receive critical messages every now and again from a recently arrived-to-Spain Brit who seeks to chastise them by erroneously saying in a pious tone: 'we are immigrants, not expats'.
Expats (expatriates, having left the patria, the home-land, rather than ex-patriots, having, er, seen the light) are simply that, a handy self-inflicted name for us Brits and other nationalities who want to join in, who live (in this case) in Spain.
We like to sententiously claim that we will learn the language, and we make some small effort to this end. But, it's hard for Brits to learn a foreign language, especially if we are not in our first flush of youth, and, especially too, if we live in an English-speaking gated community while watching satellite TV and reading worthless expat newspapers.
How many of us expats know the first thing about our host nation's culture, history and cuisine? Who do we support in an international sports event between 'our' country and theirs?
We expats don't particularly want Spanish nationalization (or, we didn't until Brexit came along) and, nota bene, we are mostly worried about whether we could still keep our British passport with dual nationality.
Not a major concern for an immigrant.
An immigrant is someone who wants to become a national.
He will learn the language, and insist that his children speak it fluently. He will, on balance, be younger than an expat, with his life ahead of him (our average age is apparently north of sixty). He will be looking for work. Perhaps some of the Brits could fall into this category, but certainly not the ones you find on Facebook.
I have an American friend of Italian descent. His parents came over from Calabria. He recalls that they would say to him over the dinner table in broken English 'you in America now, you speak American'. I know of a young fellow here who lives in rural Spain, whose father is British and whose mother is Spanish. He is said to speak two languages, learnt from his parents: these are, in order of usefulness, Spanish and Broken Spanish.
Most immigrants are known more fully as 'Economic Immigrants'. They move to a wealthier country to earn more and live better. While expats also move elsewhere to live better, they don't do it for monetary reasons, and they are certainly never referred to as 'Economic Expats'.
Howsoever, not that the subject comes up much, I shall continue to justifiably call myself (with your permission) 'a European'.