It means someone (single parent) on minimum wage with 2 children earns £10000 per year,pays £2000 tax but gets back £6000 per year in tax credit payments.Plus free education for 5 years-how is that helping the UK?
If someone comes to the UK with his children I honestly don't think that he is planing to come back to Poland.
.If they work here for 5 years on a low wage and receive tax credits then they will return to Poland with money but having contributed nothing to the UK
First of all, their contribution to the UK is the fruit of their labour; for example a house build by polish workers, a persone cured by a polish doctor or a happy customer served by a polish clerk. Polish imigrants are not being paid for doing nothing you know.
Secondly, it's not that they return with all the money the have earned during their stay in your country. They have to buy food, clothes, pay for rented houses, public transport, for doing their loundry, etc...
Oh, and I've almost forgot about the group of people in UK, that derive the most adventage from the influx of cheap polish labour, mainly the employers.