I dropped out of US high school at the age of 16 following a severe social anxiety and S.A.D. related depression episode. I later went back for my GED (Graduation Equivalency Diploma, an alternative qualification to a traditional high school diploma) via distance learning. Keep in mind that this was before the World Wide Web, and distance learning meant nothing but printed materials and no communication with anybody.
It was absolutely miserable. A lack of motivation was a major negative factor, but by far not the worst. The worst was that there was no structure to the course or materials, and there was no resource provided for helping me develop my own structure. Or really any warnings that a lack of structure might be a problem so I should look out for that.
And that's okay. Really, it was all on me. I got the GED (with all subjects between 92% and 100%), so in final analysis it didn't matter. (It ended up getting me accepted to university a year earlier than my peers, but I had the same problems as in high school with three hours of commute time to boot.) But I should have been prepared. I should have gone looking ahead of time for what problems there might be, and found solutions. I just wasn't mature enough at the time to do anything but slog through it.
That said, it wasn't all bad. There was zero social anxiety aside from when I would have to complain about course materials and I knew I'd have to start by finding out who I had to complain to. (Back then, uncertainty in contact situations was my worst trigger.) And I did have enough of a plan to know to avoid modules during the late winter months.
Technology has allowed me to work around a lot of my issues since then. It's much easier to contact people through texts, emails, and social media than cold calls back then, and online research makes it less necessary.
I can't talk about the Open University, since I haven't started there, yet. But I'm definitely preparing for distance learning ahead of time. I'm calling my preparation Stage 0, but has literally nothing to do with the Open University's Stage 0 creditless modules. I've set aside roughly half the study time that I'm planning to use during the modules, and studying preparation for the course itself. (One hour every night, with two to four extra hours as needed on weekends.) I started by going through The Good Study Guide (which the OU no longer sells, but can be found on Amazon or other places), and using it as study material, not just a book to read. Other preparations include OpenLearn modules (starting with a few badged modules, then others for fun, whatever strikes my fancy), and free training materials I've found online for course-relevant subjects. (For me, that means things like CCNA network certification tutorials and such.)
It's done two things for me. First, it has really helped me plan my time and my distance learning better. Second, it's given me boatloads of confidence, as I've been testing the methods that I've learned ... on learning those methods. So the more I'm absorbing, the more I know it's working AND the easier it is to absorb.
I know that's not entirely what you were asking for, but I hope it helps.