I really enjoyed reading this story. This segment was so very sweet (and spicy, yes). I like how it was Severus who got things started--both with getting Remus in the bed and with doing other things. Remus playing the gentleman who does his best not to do anything to offend is quite in character. As such, he really wouldn't act unless given some sign by Severus that it's ok to do so (well, heh...I suppose Remus did instigate the kiss at the party, though...but still kissing is one thing while sex is something more serious).
The ending is a nice start for them. :)
(Heh, though for some reason I got an image in my head of the morning after, with hung-over/drunk Sirius, James, and Peter stumbling into Remus' flat and being all "Moony, you missed a grea-- O_O What's all this!?")