The Celtic nationalists are a major reason for that attitude. Which, by the way, won't be improved by your engaging in more Angle-bashing for hating themselves.
As a US observer with no current political insight into the issue, I do have some casual observations.
It appears that Scottish politicians and office holders would decide one way and the Scottish electorate is running the other way. That is common here as well and lets us know the mental distance of office holder functionaries everywhere.
It also appears that the electorate is doing this on a gut level set of feelings, which is probably not always the best way to plot the course of a nation. Athens was our founders cautionary observation about democracy and government by plebiscite or referendum. That being the case, it is still pretty obvious that if the gut level choice of the population is that the union is something that should not be part of their society, they are always hampered by its presence — a dilemma.
I have to agree with one thing that has been pointed out. That is the nature of socialist costs to England by a Scotland that is not pulling its weight except in what it would keep in oil revenue. The balkanizing of medium powers is going to eventually lead us to the UN becoming more powerful and dominate.
You’re saying that Celtic nationalists have dominated English politics since just after WWI? That sounds something of a stretch.