I was waitlisted last year at the Courtauld and accepted in early May. I ended up attending the Courtauld, but I have no idea how the waitlists are organized. Most likely, it depends on how the course tutor has structured their list. When I tried to get more information about the waitlist process, the admin had very little insight on how it was organized.
Congrats and best of luck! It is possible to get off the waitlist!