youdontknowme In Britain the party landscape is somewhat more varied, but except for the Lib Dems, most of the significant third parties are regional players.
The problem in the UK is that population numbers in a seat vary hugely, and the first past the post system gives us some very strange results. In the last election the SNP MPs won with on average 25000 votes. There are 59 SNP MPs in Westminster, they got about 1.3 million votes.
There is 1 Green Party MP, they got about 900,000 votes.
The current government has an 80 seat majority, which means they can do pretty much as they like. They had 43% of the vote.