When Poland joined the EU in 2004, a new wave of immigrants arrived. Now in cities like Southampton they are a major factor in the European elections

Ten years after Tomasz Dyl left his small home town near Krakow as a 13-year-old to start a new life in Southampton, his personal trajectory has become emblematic of the story of Polish migration to the UK.

While his parents earned a living picking fruit and packing flowers, Dyl learned English in the playground, launched a marketing business at 17, went on to university, and last year was named Southampton's young entrepreneur of the year. Now 23, he employs six people, is about to collect the keys to a house he has bought on a 25-year mortgage, and cannot imagine ever returning to live and work in his native Poland.

"There is a better standard of life here, and the UK gives you more chances. It's fantastic to see the number of Poles starting their own businesses," he says.

Ten years ago this week, on 1 May 2004, Poland joined the European Union along with seven other eastern European countries. The UK was one of just three member states that allowed the new EU citizens immediately to work without restriction within its borders, with the then Labour government estimating that around 13,000 Poles would move to the UK.

Actual numbers wildly outstripped forecasts. The 2001 census recorded 58,000 Poles in the UK; by 2011, the figure had risen to 579,000. Since the beginning of this year, migrants from Romania and Bulgaria have swollen Britain's eastern European population, although as yet there is no reliable data on numbers.

This influx, and the issues that arise from it, form a central plank in Ukip's campaign for the European elections on 22 May. A poster unveiled on hundreds of billboards across the country last week shows a British builder (who turned out to be an Irish actor) begging for small change. It declares: "British workers are hit hard by unlimited cheap labour". Another says: "26m people in Europe are looking for work. And whose jobs are they after?"

Ukip leader Nigel Farage said the campaign was a "reflection of reality as it is experienced by millions of British people struggling to earn a living". A poll last weekend forecast Ukip to win 27% of the vote in next month's European parliamentary elections, three points behind Labour and five ahead of the Tories.

Ukip's focus on eastern European immigration has put mainstream parties on the defensive. Labour has acknowledged its 2004 forecast was wrong. "We should have looked more at the impact on low-skilled jobs and pay," shadow immigration minister David Hanson wrote on the LabourList blog earlier this year. He said immigration must be managed and controlled, adding: "We have listened and learned."

But, says Jonathan Portes, director of the National Institute of Economic and Social Research and a former government economist, "overall, the experience [of Polish immigration] has been very positive. Poles mostly came to work, they got jobs, they contributed to the economy, they are less likely to claim benefits. We know from several studies that the impact on employment for native workers was small to zero. There has been some impact on wages at the lower end, but it doesn't seem to have been very large."

Not so, says John Denham, Labour MP for Southampton Itchen, who wants a more active political response to issues around immigration. Day rates in the local construction industry fell by up to 50% initially following the "arrival of a large group prepared to work casually for relatively low wages" in 2004, and fuelled a boom in labour agencies, some geared exclusively to eastern European migrants. "The sense that migration is associated with downward shift in wages is quite widespread," he says. More generally, the addition of around 15,000 people to a city of 200,000 following 2004 "meant a very big and visible change to its fabric and nature".

Along Shirley High Street, an area with a relatively large Polish community, the adverts crowding the window of Malinka Delikatesy Polskie are testament to the changing nature of the locality – as well as to the entrepreneurial instincts and self-reliance of the incomers. Polish accountants, travel agents, beauty therapists, dressmakers, computer technicians and car mechanics are among those promoting their small businesses. Inside the shop, shelves are lined with Polish grocery imports; chill-cabinets are packed with sausages and cheese; Polish radio muffles the noise of traffic outside.

Marcin Piotrowski, 38, is shopping for his family before heading to work as a housekeeper at Lymington hospital. "My bosses ask me if I have any Polish friends needing jobs," he says. "They want us because we work hard. Not many English people want to do this job, working nights and weekends." Piotrowski came to Southampton eight years ago, and has no intention of returning. "I've bought a house, I have two children at school. I'm happy here. I don't even go back to Poland for holidays."

At SOS Polonia, an advice centre established 10 years ago by Barbara Storey, a Pole who has lived in the UK for more than 20 years, migrants were initially "mainly male, fairly young, and single – those old enough to be disillusioned with Poland but young enough to try something new. Then their wives or girlfriends came, babies were born. Now we see grannies coming to look after the children while the mothers work."

Sunder Katwala, director of the British Future thinktank, says most Poles come with the intention of staying two or three years, to save money from higher wages than they could earn at home. "But life happens" – better or permanent jobs, mortgages, marriage, children – "and more people stay than expect to."

A survey carried out by British Future last December on attitudes to Polish migrants in the UK found that 55% of those questioned agreed Poles "work hard for a living"; 54% said they "make a contribution to Britain"; and 57% said they "don't cause trouble in my community". Only one question, on whether Poles made sufficient effort to integrate, got a negative response, with 35% saying they did against 40% disagreeing. "There is an anxiety among the public about how we handle immigration generally, but most people's immediate experience is OK," says Katwala.

Ukip disagrees. On a brief tour of her housing estate in Shirley, local activist Val Aston, 61, lists the problems that she says result from her Polish neighbours: overcrowded schools and health centres, traffic congestion and parking on double yellow lines, litter, noise, excessive drinking, urinating in public, the sound of Polish being spoken on the streets, new private housing developments. One street is regularly blocked by enormous lorries delivering supplies to the Tani Sklep supermarket, she adds. Has she ever been inside the shop? "No, there's no reason to, I don't eat Polish food."

Pearline Hingston, the local Ukip chairman – and herself an immigrant from Jamaica as a child in the 1960s – presents the party's position. "What we have is open-door immigration from Europe. This is a massive issue when we have one million unemployed young people. I'm not against immigration – I'm against uncontrolled numbers, no checks on the quality of people coming in and the impact on the local community. The government's policy of open-door immigration is bad for this country, and here in Southampton we are feeling the pressures of that policy."

As an aside, she adds that "many eastern Europeans are racist to people like me, who have built up the NHS and transport infrastructure in this country. That makes me very angry."

In a nearby cafe, Peter Slack, 71 – born and bred in Southampton and formerly a regular Labour voter – says he will back Ukip in next month's elections. "I'm up to here with it," he says, pointing to his forehead. "I've never met one person who likes the Poles. They come over here and get more rights than local people. The noise, the booze – it's disgusting. But if you say anything about immigration, you get accused of being racist."

Katwala says that Ukip's views resonate strongly with an older generation, "particularly former Labour voters who left school at 16 and feel left behind by today's mainstream parties". In contrast, he says, for young people a diverse society is normal. "There is a generation gap on immigration and in the end the younger generation will win this debate."

Meanwhile, the city's Poles are putting down roots and channelling money into local economies. "We buy coffees, we drive cars, we rent houses, we go to the supermarket. What would happen if we left tomorrow? Who would bake the bread, paint the houses, clean the streets?" asks Storey.

Tomasz Dyl is clear where his future lies. "My mother and father talk about going back to Poland, but I can't see it happening." His father now runs his own decorating business. His sister is a commercial bank manager and homeowner, with a three-year-old British-born child. And Dyl is going nowhere. "My life is here. I have family, a business, and soon a house. I'm a happy guy."