"What they did" was strike a bargain to try and fix the voting system to make it more representative in future. The two major parties combined forces to campaign against more representative voting, because they were happy when it was just the two of them. The flip side of the bargain was that they'd vote alongside whichever party took them up. Because of that bargain, they didn't really get to vote in a representative manner. Who knows when would be the next time they'd hold the balance of power to try and effect voting reform?
And no, they didn't get 'good representation' anyway. They got 9% of the seats on 23% of the vote when they went into coalition, and in the last election, got 1% of the seats on 8% of the vote. Even as a junior party holding the balance of power in a coalition, they didn't have the clout they should have, from a percentage-of-votes-cast perspective.
But regardless of how you slice it, it's still a clear example of how a FPTP voting system ends up in a two-party political system.