There were certainly negative outcomes from that, but I’m not sure it led to political instability, and a shift of power toward an under-represented class that represents the vast majority of the economy certainly wasn’t a concentration of power.
It was a crazy amount of political instability, a G7 nation went completely bankrupt and defaulted on its national debt, imagine the US doing that. And, the Winter of Discontent led to so much political instability that it completely destroyed an entire political party and ethos - British Attlee-style far left socialism. The Labour party was pretty much annihilated, and wouldn’t see power for 20 years, and even then, only because it was completely remade in Thatcher’s image as New Labour by Blair. It wouldn’t be until Jeremy Corbyn that anyone even remotely tried on those same policies with the electorate again, and he was soundly defeated.
The leftist, socialist style government of Attlee, Wilson, and Callaghan had their hearts in the right place with their policies: government built lots of housing at a huge loss in order to give the masses affordable housing, the government nationalised many industries and utilities (such as 100% ownership of all trains, water, electricity, coal mining, but also auto manufacturing and aerospace), all of these nationalised industries had huge and very powerful trade unions, taxation on the rich was massive (this is why all the famous movie stars and musicians like Mick Jagger famously left the UK and moved to the USA in the 70s. Only Oliver Reed remained). There was even a wealth tax. Government provided healthcare was established by Attlee.
Basically all of the things leftists like Sanders and AOC want today, we had them in 70s Britain, and it did lead to “political instability” because it led to national bankruptcy, and a huge brain drain as millions of young Britons went abroad to find opportunities (many went to Canada and Australia).
The only thing that has survived from those days is national healthcare, but it’s an utter catastrophe these days due to the slave labour wages it forces on its workers with no ability to strike (they technically can strike, but it doesn’t matter, because the government can force them to accept any new contract regardless, which they did in 2016).
