Interesting thoughts. Most expats living in Spain are retired one way or the other (either state pensioners or early retirees on occupational or private pensions).
Whichever way it is they have contributed to British society and to the social security system for a lifetime.
By your reckoning, they should lose their lifetime’s contribution and while left penniless should be left to freeze in -10C Mediterranean winter nights. Very noble indeed. If my recollections from my early history lessons are anything to go by Joseph Stalin had very similar views.
Oh…nearly forgot, why should all these people who worked all their lives for their county be allowed to have a say in its future? That would be a travesty really would not you say? Incidentally, do you happen to have an axe to grind?