The Motorcyclist's Guide to Scotland book - J.G. Ferguson
As it seems a popular idea, here is the first route, The Solway and Carrick Coasts, at 250 miles.
The route is basically a triangle: Dumfries > Stranraer > Ayr > Dumfries. I asked BaseCamp to give me that route, which it did in seconds. I then dragged (elastic band'ed) the magenta line to take the roads the book's route took. I then deleted Ayr as the route does not go into the city itself, whereupon the magenta line corrected itself perfectly. I had to force BaseCamp to take one of the smaller roads and / or switched the map into routable Open Street Map. I have added the two suggested excursions (the little green add on) and the hotels and eateries. Several of these I had to create manually. The route creation is quite quick, it's adding in the bits that take the time but once done, it's done.
As with Ireland, I might well recommend that bods do load the UK OSM map into their Garmin device, though (subject to individuals' preference settings) the route should run OK without.
https://www.dropbox.com/s/2507r0yfntlb9cr/The Solway and Carrick coasts.GPX?dl=0
Whilst creating the route and looking at the map, there are some little roads that I might take instead of the way the author goes. But, that is not the point of the book, which is to give bods some ideas (and pretty good routes) to try for themselves. There will always be "You have missed the best...." type observations but so what.