I'm not accusing anyone of xenophobia--don't know enough about internal British politics to do that. In the U.S. it is a factor (which is odd, considering we are a country made up of immigrants--except for Native Americans). And I'm not an economist, nor am I a demographer. I just know that a declining birth rate, below the replacement rate, is generally not considered a good outcome--without immigration. Besides less workers to do work in an increasingly grey population, there are less people paying taxes to support the services the government provides across the board. More cynically, there are less people to fight in armies (terrible thought). I just looked up the statistics on Ancient Rome. It seems before its decline, the empire suffered a decline in birth rate to the extent that the emperor tried to offer rewards to women to have children.
As for persuading people to have children: It's more than making child-rearing affordable. In a culture where people are confident their children will survive childhood, there is little incentive to have more than one or two children. Children aren't merely expensive--they're inconvenient. The replacement birth rate in the U. S. is 2.1. Most people I know don't want to have more than two children. I certainly didn't. I would say it is not unusual to have one child households. Having children is especially inconvenient to the woman. What if her relationship fails? Inevitably, the woman suffers a decline in economic security...this insecurity lasts into old age.
Maybe a decline in population (native population) is good, as you say. I don't see it, but then, as I said, I'm not an economist or a demographer.
All of that aside--it seems you are happy, @mobbs, happily married. I'm very happy for you :)