Ashliman's Folklore and Mythology Electronic Text is a section of his larger companion to Folk and Fairy Tales. In it you will find a number of tale types and various stories (with Ashliman's sources).
The Internet Archive is an online repository that holds many recordings, print materials, scrapbooks, and other media. You may find transcriptions, audio, or other materials related to your story on this website.
A database of scanned ballads from England which can be searched by motif. The database also allows searches in the English Short Title Catalog (ESTC). The majority of the materials are 17th century and later.