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Beyond the continuing stories about asylum seekers and their desperation at Calais, the fact remains that vast majority of non-EU migrants, an expected half a million people this year, are not in this category. So how do those who come to work and live in the UK qualify? And how have they got in?

Skilled workers

The greatest number of migrant visas, nearly 169,000 this year, are tied to people who come to Britain for work. Before they get their visas there has to be a job offer.

Beyond this, applications for leave to remain are decided on a points system based on factors including previous earnings, qualifications and age.

Josy Joseph, a skilled nurse from Kerala in south India, works in an intensive care unit at a hospital in Kent, after four years at nursing college, a two-year internship and a year working in Saudi Arabia.

Image caption Nurse Josy Joseph says that new visa regulations means she and her husband may move to Australia

Josy expects to be forced to leave in 2017. New regulations mean she'll be allowed leave to remain only if she's earning at least £35,000. For all her training and experience, a salary like that is out of her league. And her husband, who has an MBA and works in a fast-food restaurant, will have to go too.

Josy thinks they'll go to Australia where she says specialist nurses are welcome. She agrees with the head of NHS England, who says that new, tighter visa rules are squeezing out the likes of Josy and simultaneously increasing pressure on the NHS.

"Either they'll be under a permanent staff shortage or they'll have to hire agency staff to cover the positions. They are going to lose the nurses, they'll have to replace them, they'll have to train the new staff. And we are taking all the skills with us wherever we go."

Students

This year 280,000 non-EU citizens will enter the UK on study visas. By far the greatest number, around 80,000 of them, will be Chinese.

One of these is Cherry Yu Qiu, a 23-year-old from Shanghai who's just finished her Master's degree at Goldsmith's College.

Image caption Former student Cherry Yu Qiu is hoping to work in media or PR

She now has a maximum of four months to find a job and a visa and is looking to work in the media or PR.

But if she does go back to China she'd like an employer who'd send her back to Britain.

"We call it seagull. Like a half a year in Britain and half a year in China. Young graduates, if they go back to China, they are going to be turtles, they can only stay in the sea, they can never get used to the environment. Of course I'd rather be the seagull."

The super-rich

For wealthy people, the route to UK residency is straightforward.

Yulia Andresyuk, a lawyer with a London firm which helps the super-rich get residency in Britain, says the basic qualification for a Tier 1 investor visa "is [the] ability to show that you have £2m. Once you receive your visa you would have a certain amount of time, that's three months to invest it into the UK in a certain way. That means investing into government gilts or bonds, buying shares or giving it as a loan to a company operating in the UK.

"Initially your visa is given for three years, then it can be extended for another two. After the five years that you have lived here you can apply for your permanent residency."

Image caption Lawyer Yulia Andresyuk works for a London firm which helps wealthy people take up residence in Britain

But the amount invested, she explains, speeds up the process. "If you invest £5m you can apply for your permanent residency after three years. If you invest £10m, you can apply for permanent residency after two years.

"Those people are tax residents here, they have to pay taxes. They're setting up companies here for creating jobs. I think they are very beneficial to the UK."

There were nearly 1,200 visas issued to the super-rich last year, not exactly swarms but double the number in 2013.

Backpackers

More than 20,000 people living in the UK this year will have Youth Mobility Scheme visas, which are valid for two years. They need to be aged 18 to 30 and have £1,890 savings. They come from a mixed bag of countries including Australia, New Zealand, Canada, Japan and even Monaco.

One of them, Australian Nate James, became a waiter in London.

Image caption Australian Nate James has returned to the UK after discovering that his grandmother was born in Sheffield

"I was working in a restaurant on the Thames and every day I would see something amazing go down the river. Every day something crazy would happen and I really loved seeing that."

In the evenings Nate took a short course in audio engineering. After his visa came to an end, he tried to get a study visa. But, as the private college he attended was not registered for foreign students, he did not qualify for one.

So, as 2014 dawned, Nate was on a plane back to Oz. But he wasn't giving up on his dream.

Descendants

For those with British ancestors, the door to the UK is still open.

A UK Ancestry visa, allowing someone to work in the UK for five years, is available to Commonwealth citizens with British (and in certain cases Irish) grandparents.

After five years, the visa holder can apply for an extension or to settle in the UK permanently.

Three weeks after being thrown out in January last year Nate, the Australian backpacker, discovered that his grandmother had been born in Sheffield and "immediately applied for ancestry to come back and finish what I'd started".

Just over 4,000 of these visas were issued last year.

Entrepreneurs

The UK also provides visas for those who want to set up or run a business in the UK.

Natalie Meyer, a 26-year-old Californian, was a postgraduate student at the LSE. But, with new rules allowing postgraduate foreign students just four months to look for work and an employer to act as sponsor, she decided to apply for an entrepreneur's visa.

Image caption Entrepreneur Natalie Meyer says the jobs she has created will be lost if she has to leave the UK

The Home Office issues only around 1,200 of these annually, imposing tough conditions.

Natalie needed a big idea, a minimum of £200,000 to invest in it, and the long-term commitment to take on at least two employees. With a family based in Silicon Valley, she used their connections to set up a software business in Britain and organised a second enterprise, offering "cultural insights, professional introductions and market research for Japanese companies entering the UK and vice-versa".

Her visa runs out in March and she has applied for a two-year extension, but is feeling stressed.

"I've created jobs and if I'm not allowed to stay, those jobs that I've created will actually disappear. So it's actually beneficial to the UK for me to be here."

Family

It was an arranged marriage which brought Pragati Gupta to Swindon two years ago. She'd met her husband Aviral Mittal, a micro-electronics engineer, via an online matchmaking website. They're both from India but he's a British citizen and has been in the UK since 2000.

As Pragati puts it: "I was looking for a match and he meets my requirements." She says she always wanted to go abroad and after the wedding, back in India, a Family Visa, available to a spouse or child of a UK citizen, entitled her to enter the UK. There will be just over 35,000 family visas issued this year.

Pragati is delighted with the UK - she says life is more fun and exciting here. She's also pleased with her husband, saying he's humble, down to earth and family-minded and that "you make a match but then you start talking and the love develops".

The Report: How To Get Into The UK is in BBC Radio 4 at 20:00 BST on 15 October 2015 and available later via podcast.