Zonker you may be aptly named if you consider such a autumn/winter voyage. Especially since you say you haven" zero" ocean sailing experience.
As to training . As a former instructor I would not agree that the Day skipper
is not a valuable cert. it's a 5 day on water
course and covers a lot of ground. More then enough for a beginner.
After that I'd suggest ignoring yacht master coastal, just go mile building over time to get enough to do the YM offshore
exam. It helps to do the shore based course as well . I would recommend a weeks YM exam prep course, with the exam immediately after that.
BUT. Take your time mile building. Doing it all in one go misses the point. The issue is to build experience. Try different environments , different boats etc. what the examiner is looking for is can you skipper
a boat , not that you can reel of information. This is what many forget. You need experience of command and exposure to lots of different sailing environments.
pS don't go round Scotland
in the winter. I'd prefer not to hear about you on the news.