Perhaps one of the Jacobite invasions succeed, although their is later an overthrow of Bonnie Prince Charlie's regime, the result being a SEVERE backlash against the Scots, who are seen by the English as the traitors who bought absolutism and popery back to Albion's shores...
Better idea (IMO):
Charlie's 1745 invasion succeeds. The Stuarts are restored, with a French army to prop them up.
The Stuarts, being pious Catholics, start work to restore Catholicism in Britain. They are semi-clever about this, and actually succeed in England, at least to the extent of forcing the C of E to merge back into the RCC; the C of E being not very different from the RCC in doctrine and practice.
However, the Kirk of Scotland is Calvinist, and utterly unreconcilable with the RCC. The Stuarts, being autocratic gits, try to apply the same program as in England. When it fails, they resort to increased levels of coercion.
The government mandates religious discrimination against Scots Protestants, producing ever increasing levels of resentment.
With French backing and Irish goons, the British monarchy holds control of Scotland, but by 1900, Scottish nationalism is a violent force.