Britons with serious, sometimes terminal, illnesses who live in the EU say they have no certainty about how or even whether their healthcare costs will be covered after a no-deal Brexit and are suffering a “living nightmare” of anxiety and despair.

“It’s like a death sentence,” said Denise Abel, who moved to Italy in 2012. “It’s all you think about. I feel abandoned, betrayed and furious. There are no words for the rage I feel. We’re the collateral damage in the government’s war with the EU.”

The UK government announced last month that if Britain crashes out of the EU without a deal the estimated 180,000 retired British nationals in the bloc whose healthcare costs it funds would continue to be covered for six months.

Most of the 1 million Britons in the EU are earners, so pay into the health systems of the EU member states they live in. Their healthcare arrangements should be unaffected by a no-deal Brexit.

Denise Abel. Photograph: handout

But pensioners, who paid social security when they lived in the UK, are part of a reciprocal healthcare scheme, S1, under which the NHS reimburses the cost of their treatment – and which will cease to exist after a no-deal Brexit.

“They feel like they’ve been kicked in the gut,” said Kalba Meadows of the campaign group British in Europe. “A lot of them are pretty vulnerable; it really wouldn’t take much to guarantee their rights until bilateral reciprocal arrangements are in place.”

The government was urging pensioners to sign up for their local health system but this was often not possible or too expensive on a basic UK pension, which is worth 20% less in euros because of the collapse of the pound since the EU referendum in 2016, Meadows said. Private health insurance was also beyond the means of many retired people, who are likely to have pre-existing conditions.

“They are left with the very real prospect of having no healthcare,” she said. “And in many countries, without healthcare you are no longer legally resident. There’s really a lot of fear. We’ve had hundreds of people contact us. Many are elderly, some have terminal illnesses – they are genuinely petrified.”

In March the government also pledged, subject to reciprocal agreements with EU27 states, to cover the costs of treatments that begin before Brexit day for up to 12 months. But the announcements have done little to relieve the mounting anxiety of many retired Britons on the continent.

Valerie Chaplin, 68, moved to southern Spain with her husband, Eric, soon after he retired nearly 20 years ago. Diagnosed last year with breast cancer, she has had two major operations and radiotherapy and will be on medication for five years, with no right to healthcare guaranteed beyond the end of next year.

Valerie Chaplin.

“It’s like a living nightmare,” she said. “You can’t get it out of your head; you have to keep busy or you’d just sit and howl. There’s no way I could ever afford to pay for private healthcare, or even to join the Spanish system. Eric is 87 now; he has high blood pressure, high cholesterol … I just feel completely abandoned.”

Monthly contributions to the Spanish healthcare system covering just “the basics” would cost the couple €165 (£147) each, said Chaplin, a former nurse. “My treatment would be €425 a month. We live on €1,600. What I dread most is something happening to my husband – I’d be down to about €600 a month.”

The couple could not afford to return to the UK even if they wanted to, she said: “I know some Brits will go back, and have gone back. But we have nothing there and our house here is worth €50,000. We’ll just stay on, without healthcare, until we pop off. It’s like our death warrant has been signed.”

Abel, a retired psychologist who will be 63 this month, moved to Norcia in Perugia, Italy, with her husband, a specialist petrochemicals engineer two years her senior. As a worker posted temporarily to the EU and continuing to pay UK national insurance, he was initially covered by the S1 reciprocal scheme, she said.

“He started to get less work after the referendum, because clients were worried he wouldn’t be able to travel and work across the EU,” she said. “Then last summer he was diagnosed with Parkinson’s. Because he hasn’t been able to work, he has now lost his S1. We have no more cover.”

As EU citizens, the couple cannot currently pay into the Italian healthcare system, and because of her husband’s condition they have been quoted a premium of €13,000 a year for private health cover. After Britain leaves the EU, Italian social security contributions could be €3,500 a year.

Eric Chaplin.

The couple are paying out of their own pockets for Italian GP visits, scans, neurologist and physiotherapist appointments and all medication – and cannot move back to the UK because they are housed in a 40m2 cabin after their home was destroyed by a major earthquake in 2016.

“The irony is, with his medication he is now well enough to return to work,” Abel said. “But he won’t qualify for an S1 form until he has a full year of UK social security contributions, by which time the scheme could well be defunct and he will be due to retire. It’s quite desperate.”

Abel was bitter. Italy was now their home, she said: “I don’t recognise my country. All the Brexit discussion is about the Irish border, trade, the economy – but what about us? The focus should surely also be on people. Brexiters say we must get it done, do or die – I say, who is most likely to die?”

In south-west France, a couple of former engineers who asked not to be named said their situation was becoming “increasingly, and incredibly, stressful”. After leaving the UK in 2007 when the husband, now 72, retired, the wife, now 63, was diagnosed with stage 4 breast cancer that has since spread to her spine.

“The treatment has been brilliant,” she said. “But my oncologist has asked who will be paying for it after Brexit. The pharmacist has asked the same about my medication. Of course, they may not be right – but nobody knows. It just gets into your mind. I’m constantly running through scenarios, and it’s driving me round the bend.”

While eventually Britain would be likely to conclude bilateral reciprocal healthcare agreements with EU27 states in the event of a no-deal Brexit – and has already reached a temporary agreement with Spain - there is, more than three years after the referendum, still no certainty about how long this will take or what will be covered.

“I’m a planner, I like to mitigate, and now I simply can’t do that,” the wife said. “My husband’s S1 – and mine, eventually, when I reached retirement age – was one of the reasons we felt able to move here. Now we don’t know what the arrangements will be, what it will cost, how we’ll be able to pay … No one can tell me.

“What happens if the pound tanks again? The strain is really unrelenting. You lose sleep over it. You just want it to go away - and then every once in a while, it just ratchets up a notch. And the worst is, they don’t care. They just want to deliver their mantra. We’re just collateral damage.”

A spokesperson for the department for health and social care said: “Our priority is to secure the continuation of reciprocal healthcare arrangements, so UK and EU nationals have access to medical treatment in the same way they do now.”

An offer had been made to all EU member states to maintain reciprocal arrangements until 31 December 2020 in a no deal scenario, the DHSC said, and some member states have already prepared legislation.

The government’s offer to fund existing UK-insured individuals in the EU for a further six months after Brexit was “aimed at providing people with time to make alternative arrangements for their future healthcare cover”.