[He does have Ianto and that means that French kissing is just about the naughtiest thing he can get away with with anyone else, and she doesn't have Derek any more and he wants to give her something to enjoy. Without the restrictions imposed by their wardens, he'd be offering a whole lot more, Ianto or no Ianto, but this is all he can give her (in this regard).
So he grins, very sure she'd tell him no if she meant it, and leans in, one hand coming up to cup the side of her head as he presses warm, slightly parted, lips against hers.]