We had a referendum on the alternative vote system - and it lost. And yes I'm aware it's not PR, but it's a start. Then the Lib Dems - whose policy is electoral reform and more coalition governments - got slaughtered at the next election for being in a coalition government.
And quite frankly I think for most non-voters it's an excuse. Nobody wants to say, I can't be arsed to think about the issues and walk the half mile from my house to a polling station. So if asked, they say that "they're all the same" or "they're only out for themselves" or some other self-justificatory bullshit.
Find someone to vote for, then maybe they'll grow their support and others will join you. Or stand yourself. Or vote for the least worst, which at least gets you closer to where you want to be. And at least drags the losing parties closer to your position, as they try to recover from losing.
Politics is like the Rolling Stones said. You can't always get what you want.