Ok, thanks for that.
Here's the population of the UK since we were born:
You must log in or register to see images
If you're looking ahead at sustainability, you must accept that by taking in large numbers now to service the current population, you are simply deferring and exacerbating the problem. In 30 years time, those coming into the UK will need servicing and so you start again, with a much bigger density of population.
For me, you have to calculate what is the optimum population of the UK that maintains quality of life and protects the natural world, and work within that figure.