This is a sequel to Not My Beautiful House, which is the one where, during the NFA battle, canon!Spike and the Spike from Bittersweets saga get switched. Canon!Spike spends some time in the Bittersweets-verse where he is startled to find that Sunnydale flourishes, the Scoobies are his friends, he's husband to Buffy and a father to Jem -- and most of all, that he's all this in his soul-less state. When he finally encounters Bsweets!Buffy, they have an informative and sharing experience, but she's shocked at what he says about his soul, and his apparent disappointment at her for accepting him without one.
The sequel deals with the aftermath in their relationships for each Spike/Buffy couple following this dimensional cross-over, and what happens when all four meet again.
Parts 1-9 of NOT MY BEAUTIFUL SEQUEL are accessible here. herself_nyc_fic is now an open comm; anyone may join as long as they are aged 18+.