Gromit: "True, the system works against them, but the fact they are a minor party is more to blame for their lack of success."
It's hard to say exactly what the fortunes of a party like Ukip (or the Greens) would be in a different system as voter mentality would probably be different as well, but then in some sense this is also the point. The current system virtually forces voters to choose between one of two candidates for any seat, and one of two parties for the overall government. And many parties know this, and campaign literature is rife with "it's only us and the other lot with a chance of winning, some other party is well out of it, so you are wasting your vote if you pick them" messages. So the voters know this too, and it's very hard to persuade them in enough numbers to buck the trend and pick an outsider candidate.
So yes, Ukip are a minor party still, but the system is far more to blame for this than people are prepared to admit. Why waste your vote on a no-hope candidate? Of course, if enough people wasted their vote that way then the outside would win after all, but you can't know what other people are doing in the ballot box so any one voter can think "well, may as well keep Labour out" and not bother voting Ukip (or "no point picking Green, the Tories or Labour will fight it out and I don't want Tories to win" from the other side).
The electoral system is letting down voters by imposing this de facto two-party system (or two-candidate system at constituency level), reducing the amount of practical choice available. Any fair system ought to give voters the realistic sense of being able to vote for their actual first choice without feeling like they are wasting their vote in doing so. That could mean PR, that could mean multiple rounds of voting, but whatever it means we should stop pretending that it's somehow the Green Party's, or Ukip's, fault that they can't break through. They don't have a chance in the current system.