It seems to me that Susan's character development would benefit from seeing something with Mrs. Goodwin. Although what she does with that information will be most revealing. Currently, Susan seems to be the most estranged from her mother of the four of them. Would seeing this make her feel closer to her mother (as they may have more experiences in common than expected, not that Su can admit that) or would she play the spy and store the information away as leverage? For all people think of Edmund as the most emotionally repressed, I consider Susan the most ruthless and manipulative (which I don't mean quiet as negatively as it sounds). I do like the groundwork you're laying with Susan's difficulty speaking of Narnia. Her reaction to the whole mess is intriguing, and the kind of self-inflicted wound that will end up hurting more than just her.

I do also love that Helen thinks of Ambassador Halifax as "His Lordship the Penguin"! And that she's realized that Susan will be off somewhere soon.

John's culture shock upon return would make an interesting story if you end up exploring it (I recall mention of a scene with John and Edmund in a pub?) Especially if Helen has reconciled her feelings about her current situation to the point where she really has very little use for him at all. Right now I get the impression that she at least thinks that things *should* be better between them.