OK, thank you for agreeing with me one the importance of teaching people to evaluate information more effectively.
As for your question, I would need to know exactly what you mean by "overpopulated" before I could agree or disagree, as it's quite a nuanced issue. Are you talking about the whole of the UK or just some parts?
I certainly agree that our economy is far too centralised in London and the South East, and that this creates overcrowding in some areas. It would be great to see a government with a strategy to rebalance our economy to encourage people to spread out into areas which are much less densely populated.
I also agree that our public services are woefully underfunded, and that this can create perceptions of overcrowding which could just as well be regarded as underfunding. I used to live in a country with a significantly higher population density than the UK, but there was strong investment in infrastructure and public services etc so the quality of life was excellent.
We have also built too few houses over the decades, and the wrong kind of houses, often in the wrong places. There are so many unoccupied brownfield sites in our cities which could be redeveloped into affordable housing provision if only there was the will to do so.
There are so many factors which feed into this debate, as it isn't just about raw numbers of people - it's about what types of people, how old they are, whether they can work, what skills they have, what gaps we have in the labour market, how people are distributed across the country, how public services are funded and delivered, what housing policies are in place, what environmental policies are in place, what specific strategies we have in place to manage food security etc.
It is such a complex and multifaceted question that a simple yes/no answer isn't really of any value.
ETA apologies, this was in response to @Walkyrie , I forgot to quote.