I can't agree with that, England is the most densely populated country in Europe. It cannot sustain itself in energy or food or raw materials.
I was born in Lincoln in 1946 and the population of the UK was around 50 million, it's now 67 million.

So was the UK underpopulated in 1946? That's a nonsensical suggestion, so if it wasn't underpopulated then, an extra 17 million people suggests a population increase that has no purpose, ie we must be over populated, The population of the UK during the war was sufficient to fight Nazism with the US and the USSR help. We talk about immigration policy, but no-one, almost literally, suggests or talks about a population policy. It was a population that had more Nobel science prizes than any other country. The industrial revolution was founded with a population of around 10 million. Without immigration we'd be in a country that had a static population which is what all countries and societies should be aiming to have.

Ever person has its needs, water, food, room, a roof and a home, policing, transport, energy, health, education, etc. Every "unneeded " person is a possible unmet need.

What I do know is that 750,000 immigrate excess p.a, is totally unsustainable, if we wish to preserve the peace and contentment of those that live in the uk presently.