It has been known for years that immigrants are net contributors to the British welfare system. (For example http://www.economist.com/news/britain/21631076-rather-lot-ac..., and elsewhere too.) What's the point of repeating that old trope? It won't become any truer if more people say it.
That may be true in the present, but I think people are mainly concerned about the future. I strongly believe in a basic income, but implementing it in a country with open borders would be impossible. Same problem with the US, where no individual state can implement socialized health care, or they would be swarmed with sick people from every other state.
As for voters in the UK, I think they are concerned about future immigrants, not the current immigrant population.
As for voters in the UK, I think they are concerned about future immigrants, not the current immigrant population.