Image copyright AP Image caption Boston businesses employ many eastern European migrants - but few want to speak about it

The ebb and flow of the tide is easily measured on the River Witham in Boston.

When it is swollen the muddy banks disappear, hiding an unappealing shoreline.

The flow of people into this Lincolnshire market town is harder to fathom, its impact is less clear.

In the decade since the expansion of the European Union in 2004, thousands came from countries once under Soviet domination to work on the land and in the local factories.

There were tensions as that human flow increased.

'Scepticism'

That has given UKIP a boost. The latest opinion poll by Lord Ashcroft showed the party, which campaigns for the UK's exit from the European Union, within striking distance of taking what was once a Conservative safe seat. They have picked up support from voters who have watched their town change rapidly.

Image caption "You can alienate yourself very quickly" in a small town, says Simon Beardsley

But the businesses that have benefited from migration - and have started to see the town revive on the back of it - are reluctant to speak out.

"Below the radar there are businesses that do feel it is positive (but) in a small town, you can alienate yourself very quickly," says Simon Beardsley, chief executive of Lincolnshire Chamber of Commerce.

"Initially there was a mood of scepticism around individuals coming in and the impact that they would make on the town and the economy. Over a period of time those impressions have changed and the acceptance of migration into the town has changed.

"Without the numbers coming in, the businesses would suffer because predominantly the area is made up of low-skilled, low-wage jobs in agriculture and food processing and there isn't the indigenous population looking to take up those jobs."

Image caption Stallholder Len Evans is pleased to have seen a boost in trade

Mr Beardsley says many employers would suffer if they couldn't recruit the labour they needed and, even if they were to entice British workers to apply, the higher wages necessary would drive up the costs.

Despite numerous BBC requests, we found, with a fierce election contest underway, those employing east Europeans in large numbers all refused to speak about it.

"Most of the land work is taken up by the east Europeans now," one young man tells me in a cashpoint queue. He says those who want that work on the land, as he once did, see the arrivals as competition.

"If you were ever stuck for a job there was always land work but it has got a bit more difficult now everybody is having to work more, because they work all the hours God sends.

"The east European gangs will work for a lot less, for a lot longer, than the English gangs."

Big increase

Image copyright AP

Boston has seen a bigger increase in residents from Eastern Europe than anywhere else in England and Wales, according to the 2011 census.

In 2001, the town had a population of 55,753, with 98.5% indicating they were white British.

In 2011, 10.6% of the town's 64,600 population indicated they came from one of the new EU nations such as Poland, Lithuania, Latvia or Romania.

Asked if businesses like immigration because the arrivals had pushed down wages, Simon Beardsley answers obliquely.

"There is a supply and demand issue here in terms of the flood of labour into the market. Businesses do need the labour, without it they would struggle to do what they need to do, so yes it is potentially a lower cost base," he says.

'Happy here'

Entertaining her daughter in a play park, Jurgita - a qualified Lithuanian environmental scientist who came to do low-skilled factory work and has already been promoted - is reluctant to address the political hostility to the migrants.

"English people are good to me, so I am really happy here. I live my life and if other people want a better life, I don't see a problem that they come. If people want to work - they can do it. If they don't, they should stay at home. There is enough for everybody."

In the pedestrianised town centre, there is a vibrancy not seen in years.

"There are a lot of full shops instead of empty ones," says one male resident.

"If they (the east Europeans) disappeared now, there would be a whole street called West Street that would be pretty much empty. It's like Poland down there," he says, referring to the once-battered road that has become a totemic indicator of the town's changing character, with its array of Baltic and Polish food shops.

One British woman tells me she welcomes the broader outlook the arrivals bring to the town, but she bemoans the pressure on schools and hospitals; a concern mentioned by many here.

Policy guide: Immigration This issue includes EU and worldwide migration, border controls and rules on work and benefits.

Her friend begins to walk off, but pauses to describe her "two years of hell" living next to 12 noisy east European men who, she says, partied 24 hours a day.

Another British woman says she fears the town is divided now but she is critical of her own community's hostility.

"If I went to a different country and people were horrible to me and didn't want to speak to me I wouldn't want to speak to them either," she says.

Competing for work

Len Evans, a fruit-and-veg stallholder on the market, interrupts his sales banter to explain how his traditional customers were ageing and dwindling each year. Demand for his produce is now driven by the "fantastic" new east Europeans.

"They've regenerated the town and the market and they're very good customers and the majority are very nice people," he says with a wry smile.

Image copyright AP

"If the east Europeans weren't here, we wouldn't be here as stall holders."

The chamber of commerce agrees the new arrivals have brought a dynamism to the economy. But many east Europeans are massively over-qualified for the work they are doing and they are competing for low-skilled, low-paid jobs with British people with fewer work opportunities. They are a godsend for employers but viewed with more suspicion by those competing for work, homes and services.

Once they have mastered the language, they are likely to move on and up the professional food chain to compete in other sectors and that could imply more immigration to fill behind them.

Saulius and Laura are both highly qualified Lithuanian architects. Laura helped renovate the royal palace in the capital Vilnius and Saulius was a project manager; both lost their jobs in the economic crisis and moved to the UK.

Laura looks after their baby while Saulius works in a food factory enjoying, for now, what he calls a stress-free job with regular hours. Both see Boston as "the start" of a new UK life-journey and Laura is particularly keen to return to architecture. It is a pattern repeated in countless interviews with aspirational migrants.

'Few English people'

But there's a twist. Laura and Saulius agree their progress in learning the language and integrating into UK society has been slowed by the lack of English people around them to speak to in Boston.

"We can learn Polish more (easily) than English," says Saulius.

"There are very few English people at the factory so there is little opportunity to speak."

The migration they and others like them represent has ebbed and flowed over the years. Some locals initially resented the fact that many took their hard-earned wages and returned home with the spoils but that has given way to a realisation that many are now intending to stay.

The voters will soon have their say but the east Europeans have come ashore and the waters in Boston are settling.

But the key question "is immigration good or bad for the people of towns like Boston?" defies all simple answers.