@mpjgregoire
Right, this is a bit up-in-the-air as nothing like this has happened before.
Even if there was a Vote of No Confidence in Johnson, and he lost that vote, I believe he could sit tight. There isn't actually a compulsion for him to leave office on losing a VoNC. He might offer to have a General Election, according to his timeframe, as that would also suit his objective (running down the clock).
I fear BoJo has the upper hand.