Hot Topic is an American retail chain specializing in music and pop culture-related clothing and accessories, as well as licensed music on CD. Because of the large number of goffic and punk-related items, it is often treated or referenced as a "goth" store.
Hot Topic (also spelled "Hot Topik") features prominently in the fanfic from the very beginning, when Ebony tells the reader: "I love Hot Topic and I buy all my clothes from there." She later reveals that she has a Hot Topic "loiyalty carde." B'loody Mary and Professor Sinister are also regular Hot Topic patrons. After Ebony goes back in time, it is revealed by Satan that Hot Topic used to be called "Hot Ishoo", but was changed to its current title in 2010.
In reality, there's no evidence that Hot Topic was ever called Hot Issue, and the company's own website doesn't mention anything about this. Also, while Ebony has her conversation with Satan in 1990, the first Hot Topic store opened up in 1988, just two years before, and it was not in Britain. On top of all this, while some Hot Topics have opened up in Canada, there are no known locations in Great Britain, hence Ebony most likely could not have gone to any near Hogwarts or Hogsmeade.