Prime-ministers are seleceted by the party in power, and they are selected by a minority of that party when required (Boris losing power - out, Liz losing power - soon out), so they will make as many 180° turns - and returns - as is required by the party that was voted into power so that same party remains in power.
I would guess that in British system quite many. As the members of party have no interest to move with new election when they aren't sure they are going to win. So PM needs to end up pretty unpopular before they make any moves for replacement.
Also considering current situation, I don't think there is too many that want to be in the shoes just yet.
Yes Minister - https://www.youtube.com/watch?v=FLm2X6sFa48