I think you have summed up where we are quite nicely, the don’t knows are largely Tories that will have to be dragged out kicking and screaming to vote but will vote Tory if they vote at all.
There have always been a considerable number of "don't knows" who vote Tory, virtually every last time.
More than on the left.
These things rarely change.
Likewise good weather brings out the left, as they have fewer cars, and live in bigger built up areas.
If the sun shines, and the polls don't change...