There's a bit where Jo writes about something.
When she writes about how she got Petunia's name and that public information film I knew exactly which one it was! It used to be shown on the tv during the ads all the time in the 80s, and actually was shown again only a few years ago a few times.
So if anyone wants to see the ad/film she was talking about it's here:
http://www.nationalarchives.gov.uk/films/1964to1979/filmpage_coastguard.htm It only last 1:30 minutes.
Loving Pottermore!