Hello, I just wanted to namechange briefly and pop in and say thank you to everyone for this lovely thread! Also, reviews keep popping up on Amazon, Goodreads and Mumsnet books by people I don't recognise, so I wanted to post here to say thank you for the wonderful reviews, in case any of them are by people on here. It feels pretty incredible that people are actually READING my book, let alone enjoying it 
Re the points about motivation and Nan's rapid changes of focus, I have taken this on board. For me this was about how it felt to be a teen - being utterly consumed by one person or thing that can suddenly shift to someone else - but I could definitely have done things to make it more believable, so I will bear this in mind for future books.
The privacy issue is an interesting one too. There's a fabulous (but expensive) book, Locating Privacy In Tudor London, that talks about differences in how privacy was perceived and attained when people lived a much more communal life. (I tend to imagine Francis habitually bribing servants when he wanted things kept from his father, though.)
Very interesting to hear the stories about real-life nuns! For what it's worth, I don't think being a nun would have suited Nan at all - it's more that of the two lives she knows, it's the one she finds preferable - the nunnery represents escape from overbearing male authority rather than an actual vocation.
Re the sequel, it's underway, but I have to finish the next book (not about Nan, but about Norfolk's daughter, Mary Howard) next! There is definitely a grandmother-related backstory that I want to write, too, but that is a little way down the line.
Thanks again for reading my book 