Of the 3.7 million growth 2.07 million was due to direct immigration and the rest of the growth, 1.7 million, is due to the excess birth rate amongst immigrants, due largely to immigrants often being couples seeking a better life together and from countries where large families are the norm. Without the last 20 years of immigration the birth rate would be less than the death rate and the population would be declining.
Anyone who thinks this overpopulation is a good idea cannot be "Green" because it results in the consumption of vast amounts of resources and destroys the natural environment. Limiting population growth is the simplest and most direct way of balancing our lives with nature.
Anyone who thinks this overpopulation is a good idea cannot be a "Socialist" because much of the deprivation in England is due to poverty in the immigrant ghetto zones such as Lambeth, Peckham etc. They cannot be socialist because without the need to find several hundred thousand new jobs for incomers there would be enough employment. No true socialist would favour the employment of large numbers of EU migrants on the minimum wage.