Some great feedback from you guys! Here are my thoughts:
Kerry/Somers/Granger: The forbidden fruit issue is what's at work here. If you think about it, we haven't really seen much of Kerry's personality beyond being the doting paramour. He's got a reputation as a playboy, as it were, so in this sense, I think he's just taken by the moment. He probably doesn't even get that George is irritated with him. In his mind, he's just connecting with Somers like he's been wanting to do for a very long time. Why would George have a problem with that? Isn't George being a little high-maintenance, he might think? I don't think he's evil, or mean, I think he's just oblivious, thinking with his dick. And that never happens.
Calder/Lennox: Calder will land in Portsmouth and take a post chaise to London. He'll be there within a day, maybe 2 if the weather is bad. There is no way Belvidera can beat him there by sea.