This novel was co-written by a future Tory cabinet minister and leadership candidate over forty years ago (published in 1970, though reference to the success of devolution in Ulster indicates it was written in 1968 or before). It is the third of a trilogy of novels set in the near future (ie the late 1970s) about a Conservative government dealing with imperial retreat (I have read the second one, in which Hong Kong is handed over to China after threats of nuclear war, but have not read the first which is about Rhodesia). My introductory line was a little misleading: the hung parliament at the start of the novel comes after two Tory terms rather than three Labour ones, the SNP hold the balance of power at Westminster and so can demand devolution as the price of support for a minority government, and there is of course no devolved Scottish administration already in place. This is more or less incidental detail, of course: the most interesting departure from today's debate is that I don't think the word "referendum" appears once in the novel. Back in the 1960s, the will of the people was deemed adequately discernable from the results of elections to the House of Commons.
I can't strongly recommend Scotch on the Rocks as literature. The connection between the high politics of Westminster and the low politics of security forces fighting nationalist extremists doesn't mesh particularly well thematically, with the one connecting character being the only woman of significance in the narrative, an earl's daughter who has gone radical. It seems more of a goodbye to the characters established in the previous two books than a terribly robust story in its own right. But it's interesting as a political prediction by one of the more reflective (if not necessarily effective) thinkers in recent British politics. It's also noteworthy that the extremists defeat the British establishment and the SNP, despite having sold out by accepting devolution, end up running an independent state that others have actually fought for. It's absurdly easy to get hold of this second-hand, and rather thought-provoking reading for today's political analysts.