Hey does anyone know of a fic from way back when in which Buffy has an inner wish of some kind granted and ends up naked in spikes crypt while he's asleep and then he wakes up and they do the do?

There was also a he will forget this if you choose clause but Buffy let's Spike keep his memory.

I know it was multiple chapters and mostly just smut haha

I think it could be Forbidden by kantayra. Lovely smutty story, I read it forever ago but I immediately went to my bookmarks to search for it when I read your description of the plot. Here's a link
http://dark-solace.org/elysian/viewstory.php?sid=518