I am also re-reading BH for more insight into what on earth Bunter is thinking for nefarious purposes of my own (but haven't got very far). It's a pity the longest sustained bit of Bunter POV is to his mother and therefore unreliable evidence. I'd never noticed the end of that morning after scene until you pointed it out.

It makes Peter telling Harriet to ask Bunter about lunch and then congratulate him when it turns out he's already organised it all seem even more of an attempt at smoothing the way for all three of them. Though it is Harriet who brings up the question of Bunter in the first place. She's been worried about what Bunter would feel about it all since two days after the engagement. Has Peter only just thought about it?

As to "following the cherished creature every step of the way", apart from writing to his mother to take his mind off it, Bunter has also found and booked a chimney sweep, sourced the makings of breakfast (or did they bring their own eggs) and arranged for the delivery of the papers by a convoluted process all by eight o'clock in the morning. Did he go out for a long walk the instant he woke up and meet half the village? He's either trying desperately to prove he's indispensable or he's sublimating something. Or just trying to keep occupied until they bloody get out of bed.