CBC: The U.K. Labour and Conservative parties both have internal tools that allow caucus to openly challenge their leaders at any point as long as they have enough support. In some cases, as it was with Starmer, the leaders leave before an internal challenge is launched. But that is usually because the writing is on the wall.
…It is also far more acceptable, and even expected, for backbenchers to challenge their party leaders in the U.K.
“In Britain you have a much more robust political culture that includes challenge from within the party. It is not unusual for backbench rebellions to happen in significant numbers on all manner of policy,” MacDougall said…