LONDON >> Silvia Luis, from Portugal, is thinking of attending university in Scotland. Sandra Martinsone, a Latvian, said she might apply for citizenship or buy property. Julie Miquerol, from France, has sped up her plans to open a startup company in Spain.

They, like some 1.3 million citizens from other European Union countries between the ages of 18 and 35 who live in Britain, are hedging their bets and pondering strategies in case Britain votes to leave the European Union on June 23.

For years, Britain’s relatively vibrant economy has attracted a steady flow of young people fleeing a lack of opportunity in their home countries on the Continent. London in particular is full of young Europeans, who have helped give the city its dynamic, global feel. From entrepreneurs, bankers and fashion designers to artists, waiters and students, all are free to resettle in Britain and make their futures here without so much as a visa.

No one knows for sure what would happen to them if Britain voted to leave the European Union — their immigration status would have to be worked out in the negotiations that would follow — but the debate itself has left some of the young people feeling fearful, frustrated and even angry.

“Maybe I’m too much of a drama queen, but I feel that it’s such a bold statement against immigrants and Europeans,” said Alejandro Macias, 31, a Spaniard who lived in Germany before moving to Britain to work for an audience research company.

If Britain votes out, three-quarters of European Union citizens working in the country would not meet visa requirements for overseas workers, according to a report by the Migration Observatory at Oxford University. The impact would be greatest for workers in agriculture and the hospitality industry, it said.

There are concerns that London in particular would suffer if the flow of skilled immigrants fell. About 1 million European Union citizens from other countries work in London, a city of more than 8.5 million people.

Young Europeans interviewed for this article said they were worried that they may no longer be able to live and work in Britain. Entrepreneurs, many of whom flocked to London because of the relative ease of creating startups, said they were concerned that they may have to put their business plans on hold.

Some said they might leave if Britain rejected the European Union, while others were scrambling to apply for British citizenship or get full-time employment before the June deadline.

Rose Carey, head of immigration at Charles Russell Speechlys, a global law firm based in London, said she had seen an “unprecedented amount” of applications for British citizenship in the last few months.

“Historically, EU nationals didn’t really bother applying for a British passport,” she said. “It used to be a couple hundred a year to now five queries a week.”

There is so much uncertainty about the consequences of withdrawing from the European Union that “they just want to get the passport so it doesn’t matter what will happen” to Britain, Carey said.

She said she did not expect the government to just kick out all the European nationals living here, but to “put in place transitional arrangements to protect the people who are already here.”

Many fear that working out new arrangements, country by country, could be cumbersome and devilishly complicated. Russell King, an academic who researches young European immigrants in Britain, said there was a “high level of concern among young people” over the vote, often referred to as “Brexit.”

“They are very active in taking measures to make sure they will be able to stay, to actively prove their worth to the U.K. and to the economy,” he said. “They’re not passive and waiting to see what will happen. They are engaging in pre-emptive strategies to maximize their opportunities to stay.”

Indeed, the contortions many young people have gone through to get here may now be matched only by the schemes they are hatching to remain, even though no one really knows exactly what steps yet to take.

Luis’ path to London is emblematic of the migratory patterns of young people seeking greener pastures while much of the Continent is struggling.

She grew up in Cascais, Portugal, and was the first in her family to learn English and attend a university. Her father, a manual laborer, moved to France for a more stable job and to help pay for his daughter’s studies.

Eight months ago, she packed her bags for London because her university in Lisbon could not muster the funds to run a master’s course in the field she wants to enter: criminal psychology.

She started working at Pod, a London sandwich shop — in the kitchen first, because her English was not good — but eventually graduated to working at the cash register and dealing with customers after her language skills improved.

Desperate to stay in Britain, Luis, 23, said she hoped to be accepted by a top-ranked criminal psychology program at a Scottish university. She said Scotland was especially appealing to her because Scots seemed determined to stay in the European Union, and have threatened to hold a second independence referendum on breaking away from the United Kingdom should Britain vote to leave.

But none of that is guaranteed.

“Of course I’m worried,” Luis said, referring to a Brexit. “I want to stay here to work and have my career.” She added that friends who had stayed back home were in dead-end jobs, and that “I don’t want to be like that.”

If Britain votes out, someone like her would not be here, and may not be eligible to remain.

Current immigration rules require non-European Union nationals to have graduate-level skill sets and a minimum salary of 20,800 British pounds per year to be eligible for what is known as a Tier 2 visa to work in Britain. The government plans to raise the salary threshold to 30,000 pounds, or about $43,000, by next spring.

“The requirement of working in a graduate-level occupation, combined with the earnings thresholds, mean that most jobs in the U.K. labor market do not currently qualify for Tier 2 visas,” the report by the Migration Observatory said.

Even those with high-level skills are making plans in case of a Brexit — and even Plan B’s and C’s.

Proficient in five languages, Martinsone, 34, who is from a rural town in Latvia, started her career at Latvia’s Foreign Ministry but took a sabbatical to pursue a master’s degree in political economy in Britain in 2008.

When the financial crisis struck, she was asked not to return, she said, because the ministry could no longer afford her. She worked for several months in restaurants, but felt embarrassed by having to polish knives and forks. She used her experiences to blog about Britain’s service industry for a Latvian audience.

“It became quite depressing,” she said, “especially as I had just gotten my master’s degree.”

Yet in the midst of tough job market, Martinsone felt strangely comforted by the knowledge that other workers had good degrees, too. “I felt, ‘I’m not the only one,’ though it did not make me less eager to prove that I could be valued in London.”

She now works at a charity and said she was considering applying for British citizenship and buying property to forestall the potential consequences of a Brexit, which “would be quite dramatic.”

“If you own something, you might be treated differently,” she said.

Short of citizenship, the potential complications have some young entrepreneurs considering leaving altogether.

Julie Miquerol, 30, moved to London seven years ago from Champagne, France. She recalled how she had started out living in a room too tiny to fit even a desk. Little by little, she worked her way up, first to a bigger room, and now to a full apartment.

Today, she runs her own events company, which caters to French tourists in Britain. London is “a very tough city because life is very, very expensive,” she said. “But really, if you make it in London, you make it everywhere.”

Still, even after so much sacrifice, talk of Britain’s exit caused her to accelerate plans for a sister startup in Barcelona, Spain, where the European Union’s rules would protect her.

That the referendum is taking place at all has deeply offended many Londoners from other European countries, who are not allowed to vote and feel they have contributed a great deal to the life of a deeply international city.

“I can’t avoid taking it personally,” Macias, the Spaniard, said. He spends his evenings tearing up leaflets that call for Britain to leave Europe, he said.

“The British speak as if they’re their own continent, floating in the middle of the sea,” he added. “You’re European. Deal with it.”

© 2016 The New York Times Company