Ah me, an Iron Curtain is about to fall across the Channel, there will be thousands, nay millions of Displaced Persons struggling to get on the right side of it, people who find themselves on the wrong side will probably have to sign in weekly with the KGB and a great deal of similar crap.
Possible crap, but not, based on my experience, likely crap.
My father went to work in The Netherlands in 1967 and we joined the EEC as it then was in 1973. What I know is that my mum and I first went back and forth freely, then went to live in The Hague. What I know is that I attended The English School of The Hague, where there were children of about 40 different nationalities and a small surplus of Brits and we all went to and fro, both back and forth to the UK and all over Europe. What I know is that my father retired in 1971 and duly got a pro-rata Dutch pension and of course his UK pension also.
I was in my mid-teens. If my parents had had constant dealings with officialdom, I think I'd have noticed. Presumably they had to register residency but I suspect that was about as much hassle as registering for Council Tax when you move to another part of England. For that matter, when about 10 years later I, a citizen of the European Union, was a student in Switzerland, a non-EU country, I had to register myself as resident in the canton, that was a non-event.
Some of the fathers of my British school-mates were working for ESTEC, the European Space and Technology Research Centre at Noordwijk. I’m sure they were brilliant scientists but in terms of for instance employment quotas the question arises of whether they were conspicuously more brilliant than any member of an EEC country working in the same field: whether they could be employed only because no suitable ‘EEC national’ could be found.
There are or were other intangible elements. Language is one. French does not get you very far north of Brussels. You can survive with German or speak English. The Dutch don’t really expect you to learn Dutch, at any rate for complex conversation, though of course they appreciate it if you do or try to. I am talking about nearly 50 years ago. Fifty years ago Germans still distinctly failed to be flavour of the month; too many Nederlanders still alive who remembered having been left eating tulip-bulbs in 1945, not to mention events prior to that. Once a surly elderly newsagent broke into beaming smiles when I gave up on my school-German and starting talking English, couldn't do enough to help me.
The Dutch were pro-British for reasons both past and present: to be British in 1968 was to come from Beatle-land, Carnaby-Street-land, Quant-land, Stones-land. The past reasons were naturally more those of the older, the present ones more those of the younger. Young or old, forgetting was not on the agenda. In 1970, 25th anniversary of the end of the war, film of the liberation of the camps was screened in every cinema and The Battle of Britain, Is Paris burning? The Guns of Navarone and other war-films were regularly screened. Those this side of the water who (weirdly) dismiss such movies as jingoism, nationalism, might just switch on their brains and ask themselves what the Battle of Britain meant to those on the other side of the water.
EU countries are not, what d’you call them, rogue-states, unpredictable. We are not talking about for instance North Korea. It does not seem to me likely that people who pay or have paid the various equivalents of National Insurance will not duly get such pensions and other benefits as are due to them.
Reason tells me that those who may face a problem are those who have retired to EU countries and therefore made no contributions, that the elderly with increasing need for health-care may be deemed an economic burden. However, reciprocal arrangements exist and, since reciprocal arrangements are purely a matter of moving money around, there would seem to be no huge barrier to their continued existence. If you have paid into the NHS for 50 years, it doesn't seem overly complicated that the NHS should refund the costs of Spanish doctors treating your chronic condition. I of course am not a bureaucrat.