We have a Polish lady in our company, she's now head of marketing. She (university lecturer in Poland) and her husband (extremely respected surgeon in Poland) have moved to the UK with their children because, no matter how hard they worked or the more successful they became, the more they were stamped on by the Polish government. Regardless of their status, they were still living in a grotty one bed apartment, with very little on the horizon for their children. They are both working in the UK and paying their taxes. She was recently criticised by another colleague for taking jobs from English people. He forgot to tell her that last year his son emigrated with his family to Australia for the very same resons.
I only know her story. But we have to ask ourselves in that position would we not do exactly the same??