Hi Richie,
FEP is Frank Purslow who edited the Hammond-Gardiner Mss (now online in The Full English) in 4 volumes, mostly collating several variants, Marrow Bones, The Wanton Seed, The Constant Lovers and The Foggy Dew.
I worked on the first new edition with Malcolm Douglas just before he died and then continued the second of the 4, and am currently working on a joint edition of the last 2 books. I think he was a little optimistic over the age of the ballad, but he was writing this in the early 70s without the current knowledge we now have.