Heh it's nice that Nat did give Ann a birthday "present"; not sure it's exactly what she would've had in mind though

(It made me wonder about the practicalities of getting clothes washed in those days also, considering we're long before the days of automatic washing machines and biological powder...) But yeah, I agree with your summation of their relationship. It's kind of sweet actually, they're acting like a pair of teenagers trying to not get caught out by their parents.
Also good to see a bit more info about Nat's Latin abilities, which I queried the other day. Seems like he probably would've translated the Latin he found on gravestones later with the aid of the dictionary, it doesn't sound from today's entry like he would've been confident enough at this stage to be able to do it unaided much.
St Mary Aldenbury has an interesting history that I wasn't familiar with previously. According to wikipedia all but the walls were destroyed in WWII and these were actually rebuilt in America; there's a pic of both the church as it is now and the empty space in London where it once stood:
http://en.wikipedia.org/wiki/St_Mary_Aldermanbury