Why do areas with few immigrants support UKIP?

Here's the map (thanks to Soylent Dave):

UKIP's key message is anti-immigration, but its support comes from areas with few immigrants. Why?

• People who dislike immigration have moved to get away from it. 

This surely does happen but it is hard to believe it happens on such a large scale. After all, moving to Northumberland to avoid immigrants seems a bit extreme.

• Fear of immigration is irrational, and is dispelled by getting to know some actual immigrants.

That could easily be true. Still, do people really base their vote on a fear of something they have never met?

(I recall a friend's father - a very intelligent guy, not a bigot - talking about immigration, in Shropshire in the 1990s. We feel as if we're being overrun! he said. I looked out of the cottage window. The immemorial hills stretched out above us. No human figure was to be seen. The green fields were dotted with grazing sheep....)

• The marginal cost of the first migrant is the highest

This is my idea. Suppose that there are gains from living in a very stable community with little in- or out-migration - say because people who interact repeatedly over the long run are able to develop high trust and solve social dilemmas. (This is the standard Ostrom-Axelrod-Folk-Theorem way of thinking, in the social science literature - an idea I think has some serious defects, but it will do to stand an argument on.)

Now suppose that even a little immigration or population movement destroys that trust quite quickly. Then the places which still have these stable communities will be keen to stop migration. Other places will already have lost the stability, so it will weigh less against the countervailing gains from immigration, such as cheap or skilled labour. They will also perhaps have started to develop more multicultural forms of community, making it easier for them to integrate more new arrivals.

• Poverty

The last explanation is the simplest: UKIP thrives where people are poor, and the countryside and North-East are poor places.

It would be fun to test these rival theories. Relatedly, it would be interesting to see whether the UKIP areas actually have big recent immigration flows (i.e. changes in the immigrant stock, it is the stock that is shown above) - in percentage terms, say.

Another point about these maps is that they do not seem compatible with anti-immigration sentiment being due to squeezed public services (the "Britain is full" argument). Those squeezes would surely be tighter in urbanized, highly populated areas, but UKIP support seems to come from the countryside.