Here's a mini report from Norway. Last year the conservatives and allies lost their majority, but the Labour party was in a minority. Before the election the Labour party had a sort of pact with the "Centre party" and the left socialists. But when they came to form a government the demands of the left socialists could not be met, so the Labour Party formed a minority government with the Centre Party. But on key issues the left socialists have supported this minority government when they have managed to push it leftwards. Now had this been the UK, left wingers would have been in the Labour Party, and would not have had this leverage. PR, and no first-past-the-post are the crucial elements here. This is how the electoral system in the UK makes a left-wing government more or less impossible.