Thanks for that.
About 20 years ago I went into our local Uni library where they have almost a full set, and copied as much of the relevant ballad material as I could. Unfortuately it was something of a rush and I know I missed some entries as, like this forum, many of the entries were part of a thread. However I have a reasonably comprehensive set so if anyone has a particular query the chances are I can find it quickly as I have the NQ indexes and all the copied entries I have are incorporated into my own ballad indexes.