I have to fundamentally disagree with you here. Yes Brexit was, to many, about nationalism but what tipped the balance was the lack of democracy. Jeremy Corbyn was committed to honouring the referendum but was undermined by Starmer and betrayed by the party which was more than pleased that Labour lost the election. Brexit was a disaster because it was abused by the political class both before and after the referendum.

If there's a migration crisis in the UK it's purely manufactured by the government and its made worse by government propaganda and racist rhetoric. The racists talk only about 'the boats', a trope used by the Tories and Labour to demonise the most vulnerable in our society. Furthermore both Labour and Tories are profoundly Islamophobic.

Poverty is, of course, a petri dish for racism, crime and prejudice but its more subtle than you are portraying here. In some ways you're oversimplifying the root causes of unrest but you're also missing the obvious. Neoliberalism is in crisis & fascism serves its purposes. Brexit didn't so much embolden the far right as force division. The referendum didn't need to be so divisive. It was a plaything for the liberal elite.

What we are seeing is empire in decay.