The scale of recent immigration, the cost of living (notably housing), poor public services and rise of social media is a perfect recipe for resentment.
The scale of immigration over the last 4 years has been unprecedented. I believe over 3 million net immigrants in 4 years! When even a Labour PM says we have lost control, you have to sit up and listen.
To put into context the scale of immigration, I read more Indians came to UK in the last 4 years than the preceding 15 years. More people from Nigeria came to UK in last 4 years than the preceding 20 years.
As an immigrant myself, I feel British are generally a tolerant people, but they just can't cope with the level of immigration they have experienced in the last 4 years let alone last 20 years.
Most of the recent immigration was driven by low wage vacancies (mainly in social care) along with their dependents. Furthermore, a significant uptick in refugees (notably Ukraine) and illegal immigrants from France (predominantly men from countries with poor track record on women's rights) gives the feeling of unfairness in the system.
This level of immigration from predominantly developing countries working in low wage sectors has put significant pressure on existing wages as well as access to housing and public services.
Because of the scale of immigration over the last 20 years, there is less pressure for new arrivals to integrate. This puts pressure on social cohesion especially between some communities. There is a feeling this country has given up on hard won battles for women's rights, free speech and the removal of religious ideology in driving public policy.
Social media then feeds on the emotional aspects of the debate (eg. Unfairness of allocation of social housing or illegal immigrants living in hotels or anger over the grooming gangs) and so certain influencers gain a lot more attention than would have been possible under the old terrestrial TV model. Social media then feeds back into wider society and so resentment and mistrust grows.
OP - don't know if I answered your question, but think the issues facing UK are no different to many developed countries. I have read similar issues in Canada and Australia. The West is facing an ageing population, massive debt, large scale immigration, high living costs (notably housing), poor public services and lower living standards. There is a general depressed state of affairs in The West, so think people are angrier, poorer and less trusting of each other.