"He'd never imagined that snogging could be a form of fighting, but with Draco, that's exactly what it was. The first one to pull away would be the loser, so they kept at it until they sunk to the grassy earth, breathless but unwilling to stop."

This is EXACTLY how these two would react with a first kiss. You got it perfect! Now they have the best way to fight under their belt. (As if they haven't known that for ages. So them.)...