Whilst I too consider the planet over populated, it’s tricky to cull the number of humans without coming across as a mass murdering fuckwit. I’m sure, in time, that the planet will do something to radically decrease the number of living humans.
The U.K. is doing its bit in having its birth rate less than its death rate. Sadly, though, this will mean loads of old people with not enough young people to look after them and pay enough tax.
Therefore we need immigration. How that is done is up to each country, but as you rightly point out, we’re governed by idiots voted in by the madness of the public.