I'm from Belgium.
The winning party gets to form a government. Off course, when they simply can't come to an agreement with other parties, another party (logically the second biggest) gets a chance to for a coalition.
But following this logic the Conservative Party should get to form a government in the UK (under the assumption they win off course). If after long debating neither Labour or the Lib Dems are willing to join to make a majority, then off course a Lab/Lib government is the only option left.
Also, your last sentence. I recall a few people saying that Labour won the elections about 10 years ago and could form a government based on like 20% of the popular vote. Or was that a minority government? That sure as hell would not be possible in Belgium. 20% of the votes also means 20% of the seats in parliament. Well, there are a few side notes: the country is still devided into regions, and there's a barrier that says parties with less than 5% of the vote can't seat in Parliament. So the parliament seats don't represent the popular vote 100%, but it's a Proportional Representation system. Not a winner takes all system like France (and UK?).