The Labour party in the UK has all women shortlists, as befitting its left wing policies. It has never had a female leader, let alone a female prime minister.
The Conservative party refuses to use gender quotas, and has given the UK both its female prime ministers, who won fair elections, in which neither campaigned on a Clintonesque "vote for me because I'm a woman and that'd be neat" line.
To me, it doesn't seem like "positive discrimination" even works there, and by the way, let's call it what it is, sexism and racism against majorities. Nothing positive about it. The British Empire oppressed all sorts of ethnic majorities (in the countries that were conquered), because they believed the conquered people were savages/lesser people/etc. We don't hesitate to call that racism do we?