It's pretty weird that you hold up the fucking lib Dems as your party of radical revolution.
The fact of the matter is that we are never going to get a radical left government, regardless of the voting system. Unless you're spending time in an ivory tower of academia, you will know that the majority of people in this country are centrists of some flavour. Corbyn got massacred at the polls, and he was Labour leader. Going back you've got Foot.
The best we've ever had it is when Atlee, an ex army major who practically ran the home war effort, couched left wing reforms (foundation of the welfare state, nationalisation of coal and rail) as nationalistic. That's how we get these things through. You're never going to change the minds of British people by bombing.
If you're of an anarchist mindset, then it's far more beneficial to vote for harm reduction one day per four years, and organise in parallel outside that