The character names "Maud Bailey" and "Christabel LaMotte" refer to a special form of castle, the Motte-and-Bailey, widespread in the 11th/12th century.
A large part of Church Street in Whitby was dressed to give it the appearance of a 18/19th century fishing town. Gwyneth Paltrow insisted that the whole place was screened off so that she was not visible to the small crowd of on-lookers. Jeremy Northam, however, took time to go and talk about the film to the bystanders. Miss Paltrow also turned down an offer from the local dignitaries to meet the mayor and be shown around the town. The Whitby Gazette carried a massive banner headline declaring "PALTROW SNUBS WHITBY".
During the love scene between Christabel and Ash, the close up of Jennifer Ehle and Jeremy Northam kissing, you can see Ehle's ears are double pierced. Victorian women did have pierced ears but would not have had double piercings.
Everyone was handling rare, old documents with their bare hands. Anyone doing this kind of research would know to wear gloves to protect the fragile paper.
When Maude is in her car waiting for Roland to come out of the museum, her window is down. When he gets in the car and they begin talking, it is rolled up.
Maude: [they are standing on rocks in a river looking at a waterfall that Maude recalls in one of Christabell's poems that describes a cave behind the waterfall. Upon sharing that with Roland, he immediately starts taking his clothes off]
I know this is an awfully repressed sort of English thing to say, but what the hell are you doing?