Rich people and immigrants

Here's what I don't understand about well-off British people hating immigrants ('coming over here, cluttering up our beautiful country ...') as my occasional perusal of the Daily Mail leads me to believe they often do. Well-off people like to show off their wealth: an expensive car, a nice house. Discrete but unmissable signs that say: I have money, you know. Well, immigrants, legal or otherwise, don't come to the UK for the climate; they come because we are as a country, compared to whichever homeland they are leaving, better off -- because there is more money here. So what I don't understand is: why don't well-off people see immigrants as a symptom of our national prosperity (which, amongst other things, they are) and therefore of something of which we can be quietly proud, in the same way we might be quietly proud of a new consevatory, or a house in the Algarve -- rather than seeing them as a problem?

Personally I think of immigrants as, in the first instance, human beings. But then: I'm not rich.