Revolutions are a really bad idea IMO. They are very rarely peaceful, they tend to involve a lot of innocent people getting hurt or at least suffering, and they usually get their momentum from a passionately rhetorical cause with a mass following, which does not pan out well afterwards. The kind of person who can lead a revolution via charisma, rhetoric and ruthless devotion to the cause is not usually a great leader when it comes to the complex demands of managing a state. Then you get, at worst, a totalitarian state developing, or a power vacuum, or a mish-mash of corrupt incompetents in charge with power changing hands frequently - in other words, more of the same.
History suggests that gradual political and social change (including at grassroots level, not just in parliament) gets the best results, boring as that is. Look at Obama in the US. Plenty of people said there would never be a black president or not in their lifetime. It might have seemed impossible as recently as the 80s. But it didn't happen by revolution, but by gradual changing of opinions, the gradual reduction of bigotry through social forces, like education, legal changes and grassroots campaigns like the civil rights movement. Meanwhile, Obama worked from within. And someone who can do that, makes a leader who can then hold it together and run a stable state. (Not saying he's perfect of course, or that the US's problems are all solved - but that big changes can happen without revolution.)
I think there's actually a lot of campaigning and social change going on now, though there's an unfortunate lurch to the right in UK politics of late, but I predict that will lead to either the formation of a new properly liberal socialist left party, or labour getting a new direction under a new more forcefully left-wing leader.
Gordon Brown's referendum speech was the kind of leftiness I like to see. He actually quoted Marx directly in that speech, with no shame. And it made me think that's the kind of politics I would like to see invade westminster again. I think it will, as a reaction to the UKIP-style direction.