This is a good analysis of Darcy's second proposal, but I have a couple of quibbles.

I don't think that the point of what Darcy says is being very English, very still upper lip. I think it is a sign that he is putting Lizzy's feelings first, in stark contrast to the first proposal when his own feelings were uppermost in his mind and concern for Lizzy's nowhere to be found. And while the words lack floweriness, there is a certain romantic-ness in that conern. Darcy is not expressing feelings that would embarrass Lizzy if they were unwelcome (though once he knows they are welcome, that changes), and he makes it as easy as possible for her to refuse if she so chooses.