The Letters (the 84, Charing Cross Road Remix)
A relationship in letters, e-mails, and wedding invitations. Note: The harry potter timeline has been shifted so that the last two books occur during seasons 5 and 6 of Buffy....
http://www.tthfanfic.org/Story-31511/DragonsPhoenix+The+Letters+the+84+Charing+Cross+Road+remix.htm