I see what you mean about Roy Palmer's introduction - he certainly thought they were there, despite the entry on the EFDSS wiki I quoted.

The Sound Archive search for Burstow returns 6 items, 5 of which are folk-related (one has composer Burstow), and all mention the name in the context of notes (one not Henry Burstow).

Since the Sound Archive helpfully provides contact information, it would be easy to contact them and see if they have any more information:

    Janet Topp Fargion
    Curator, World and Traditional Music
    The British Library Sound Archive
    96 Euston Road
    London
    NW1 2DB
    United Kingdom
  
    Tel: +44 (0)20 7412 7427
    Fax: +44 (0)20 7412 7441
  
    E-mail: worldandtradmusic@bl.uk
  

The other avenue would be to see if anyone could contact Roy Palmer and find the basis for his introductory remarks.

Are you volunteering for the treasure hunt Nick?

Mick