In Boston, Lincolnshire, a key Ukip target seat, John Harris meets Nigel Farage, picks daffodils alongside East European migrants – and learns how a combination of immigration, exploitation, low wages and sky-high rents has created huge local anger. Here, Britain's most insurgent new party seems to be defying talk of a slump, offering simple answers, and attracting big local support. But is the failure of politics and economics in east England more complicated than Ukip make out?