a person who has come to live permanently in a country that is not their own
immigrant noun - Definition, pictures, pronunciation and usage notes | Oxford Advanced American Dictionary at OxfordLearnersDictionaries.comDefinition of immigrant noun in Oxford Advanced American Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.www.oxfordlearnersdictionaries.com
That'll be an immigrant then, not an "expat". as we've already covered
You can call them immigrants and I'll call them ex pats. What a great language we have.
Edit, it depends upon your definition of permanent. Most of the ex pats would still see Blighty as home and if anything got a bit dodgy would be off like a shot.