Data repair and upgrade after update
If you think the instructions are not as easy to follow as expected or need adaption in order to make them more self-explanatory (one reason why we have the videos), we are more than happy to see them improved based on user experience.
Please don't hesitate to make adjustments (after all it is a wiki) so other users can participate on the gained experience.
I'm not sure I'm currently qualified to give advice given how badly I seemed to break my install! I think the problem was the classic one of following outdated advice and relying on Google search too much.
I started with a fresh install following the video and found Composer to in fact be very good, though I think it would be helpful to be a bit clearer about it's function. I really had no idea what it was even supposed to be doing for quite a while.
I think I'm back on track now anyway, lesson learned that maybe I should keep more abreast of changes (just need to find the time!).