During the seminars for the butterflies you can clearly see female mannequins sitting with the audience.
There are no men in the film at all.
Due to budget restraints the blue and white bathroom tiles shown behind Evelyn as she hand washes Cynthia's underwear were created with stickers. Similarly much of the decadent wallpaper was printed from the web.
The Duke of Burgundy (hamearis lucina) is a small orange and brown springtime butterfly that is found in England only with a stronghold in central-southern areas and more isolated colonies in the southern Lake District and the North York Moors.
The safe word 'Pinastri' is a reference to Sphinx Pinastri (also known as Pine Hawk-moth) which is found in Scotland and England.