Katharine Briggs (1898-1980) was a prolific and widely respect English folklorist, and her books still carry weight. Her monumental multi-volume collection, Folktales of Britain (1971) is extremely useful. It was published in a less expensive abridged version, which is good - but not complete.

There is a nearly invisible question embedded in your term "English Folklore": most collections of what purport to be "English" folklore rely heavily on collected material from Cornwall in the far south west of Britain. Cornwall is regarded as one of the six Celtic nations. Its language was largely (but not entirely) lost by the 1800s but is now in revival. My analysis of Cornish folklore is that it is distinct from that of England. See for example, my book, The Folklore of Cornwall: The Oral Tradition of a Celtic Nation (2018) and see my article “The Other Side of the Tamar: A Comparison of the Pixies of Devon and Cornwall,” Folklore ,131:1 (March 2020).

Because Cornish collectors were so remarkably successful and not all other English counties are so well represented, "English" collections of published folklore frequently draw upon Cornwall, but that approach fails to capture what one can regard as truly English, and it muddies the water when it comes to Cornwall's distinct character.