I've just been watching the predictions re Johnson on Newsnight. There was disagreement about whether a no-confidence vote would come before or after the by-elections and which parties would win them.
One possible scenario wasn't suggested; I think it's possible. I think it's likely because my impression is that above everything else, Johnson will destroy what he can't have. So, if there is a no-confidence vote, followed by bad results at the by-elections, what is there to stop Johnson calling a General Election, thus denying power to those who opposed him and landing the opposition with the worst circumstances I can remember - and they are probably worse than we actually know.