I agree that Brexit is a symptom, but I think a key underlying cause, that you've not mentioned is the deindustrialization of the UK (and I include the mines in that) without ANY plan to replace the jobs and income. Not only did this impoverish huge swathes of the country, create mass unemployment, and destroy communities and the peoples' dignity, but it helped to drive the permanent trade deficit, which in turn weakens the currency, and makes the country very prone to imported inflation.
Thatcher decided that an acceptable price for breaking the power of unions was the decimation of industry - in a similar way to how Boris decided that decimating the economy was an acceptable price for Brexit (and his own personal ambition).
It may be true that the coal mines had to eventually close due to global warming, but we were importing coal for years, and paying more per ton than home mined coal - for POLITICAL reasons. Plus now the UK has so little domestic industry that you are reliant on "inward investment".