The name, UK, has nothing whatever to do with percentages. In 1603, when the Union of the Crowns happened in the person of James VI/I, only two kingdoms were involved, Scotland and England. The name created then for the new entity, Great Britain, was later extended to become the United Kingdom (UK).
It is a mystery to me how the rump of that UK - which is what would be left if Scotland were to vote 'Yes' next month - could possibly still be called "the United Kingdom", given that one of the only two kingdoms involved would no longer be a part of it.
I think it should be called The Rump!