I don't really know what to say that hasn't been said already. This is a wonderful story, moving and beautiful and heartbreaking and funny all at once. The voices are spot-on -- it's quite refreshing to read something like this, instead of the usual slashfic!dirty talk:
"But it's been a long time," said Dudley, his tone musing, teasing. "I don't reckon you can take me like this, on just a gobbet of spit."
"Can so, you shit. You just try me."
And then there's this line, made even more outstanding by the sudden shift of tense (goodness, I love it when writers can pull off stuff like that):
And he won't forget the way Dudley chanted sweetheart sweetheart against his lips, even if they never speak of it again.