"The largest source of population growth in the UK is natural growth (that is, babies being born)."
Not really.
From National Statistics Online:
"Natural change was the largest contributor to population growth until the year to mid-1999 and more recently in the year to mid-2008. Between these periods, net migration has been the main driver of population change. In the year to mid 2002, net migration accounted for over 70% of the total population change.
From 2002, natural change has increased and in the year to mid-2008 it accounted for over half of total population growth (54%). This was the first time in nearly a decade that natural change was the main contributor to population growth over a 12 month period.
...natural change contributed 220,000 to population growth in the year to mid-2008; this is more than a three fold increase from the mid-2002 figure of 62,000. This increase in natural change is mainly attributable to a growth in the number of births although a decrease in the numbers of deaths over this period has also played a part.
The number of births is increasing partly due to rising fertility among UK born women and partly because there are more women of childbearing ages due to inflows of female migrants to the UK."
In other words, over the last decade, the rise in population has been predominantly due to immigration. Only in one year did natural growth exceed the number of immigrants to the UK - and it is thought that the rise in natural growth is, in part, attributable to the inflows of female migrants.
I think the failure of any main parties to adress the issues surrounding immigration has played a major part on the rise in popularity of the BNP. I don't think the answer is to autromatically label anyone who expresses concerns as racist. I think the answer is the bring the issues into an open mainstream debate. England - as distinct from the UK - is already the most crowded country in Europe (population density 395 people per square kilometer).
Going of at a slight tangent here, but I also think that the policy of multi-culturalism can sometimes foster a sense of "us and them", and that in celebrating diversity we can sometimes emphasize the "otherness" of different cultures and communities.