After the technical difficulties (entirely at YouTube's end, by the look of it) of uploading the complete video, I am now doing it in chunks instead. I have a theory...
As I write this post initially, just one part is up (with no problems, I notice with interest!) but I shall add the later parts as they eventually get up the line and are "processed" (in YouTube parlance). UPDATE: Part 2 is now up, as is Part 3 (at last!), and these are also embedded below.