Hi Steve, there is some background material regarding the folio itself, and its present location, see in particular the relevant British Library Catalogue description for the work. Also a couple of links to works a little later than the original 1907 publication by the Rev. Clark, being this Review of Clark's publication by A.E.H. Swaen, and this subsequent set of notes on the Ballads by H.E. Rollins, from the 1917 Journal of American Folklore.

Of course you may have seen these already (apart from the BL Catalogue description, which was not easy to find).

Cheers - Tony