Unfortunately the idea that a nation needs an ever increasing population (be it home grown or via immigration) to support an ageing population is very popular – and totally ridiculous.
Strangely, the younger people eventually get old so they, too, need support in their dotage. Where do they get that from (under the current model)? Correct – an ever increasing population of younger people who, er.. eventually get old. Where do they get their support from? I think you get my drift.
The UK’s resources are already under enormous stress. And it’s no use saying there is plenty of space in the middle of Lincolnshire. There are no houses or facilities there, nor are there likely to be in the foreseeable future. To pursue policies that depend upon ever increasing numbers of people is a betrayal of the first order and one way that such a betrayal can be addressed is to restrict immigration drastically.
Of course jake will say that many companies cannot survive without skilled immigrants. Firstly, it's not just skilled immigrants that have contributed to rising numbers. A lot of unskilled and unemployable ones have arrived as well (during the time when unemployment stood at around 5 million). But in any case the so-called "skill shortage" is also the fault of successive governments too for not providing decent enough education so that skilled vacancies can be filled from within.