I liked this very much, just the right mix of drama and comedy - and "nutso" Spike's voice was perfect. I also liked the way you described Giles' attitude to the soul. I could never understand Giles' hostility to souled Spike but this:

A vampire seeking out a soul of his own volition? It had to be a trick. And even if he had? Vivid memories of Angelus, of Jenny and the rose were quite enough to haunt him. A souled vampire was an unstable vampire, and an unstable vampire was better off dust, for everyone’s sake.

explains it.
Any chance you could carry on into AU?