At which point this 2-year-old thread comes full circle; that's Lesley's own site you've just pointed to.

John's mention of Distiller reminded me that I actually have that now, so I've had a go at some of the Concordance files.  They seem to convert to .pdf well enough, though only one of the two formatted text files will convert, and of course the bulk of the song texts are in the "raw text" file, so that isn't going to help people who want the song texts in a readable form.  However, it looks as if the concordance itself is potentially more useful than I had realised, at any rate to people who also have the books.