Does Ireland work as an analogy?
Not entirely, but legally it's the precedent, a secession from the continuing UK with no need for a new Act of Union.
There's also Quebec, but that's primarily linguistic and cultural hence maybe a bit more Welsh, etc.
The SNP's preferred parallel with their mates in Catalunya is the worst of the three, and their references to the Czech-Slovak divorce are wishful thinking: The UK is not going to be dissolved, and the only share of the nation's foreign currency and gold reserves an indpendent Scotland would get would be in return for a one-for-one share of the national debt.