Ok - a bit easier and quicker way to do it. Again using Everything. This is in real time including launching etc. Without the demo bits I can do any number of files into WMP in the correct order in about 20 seconds :)

45 sec video from ripped files to WMP playlist

1 Save all your rips to a folder called (say) Ripped_Books and create as many subfolders as you want or the thing chooses to create.
2 Launch Everything and change the filter from Everything to Audio (will pick up any audio format)
3 I search for H:\ripped to find all the files in the root and subfolders
4 A quick demonstration of the problem stated earlier ie if they are all named 1 or 2 or...
5 Sort by Date Modified first to last
6 Highlight the files and (I had already created a) right click Send to WindowsMediaPlayer as the right click menu works curiously with multiple files and it was a practical solution
7 Done!