@CiaraNi Happy to be the international branch of #DanmarkSkifter!
And I (mostly) did it, before the deadline! I had to look at all the files I had in my Dropbox and decide if I could just trash them or if I wanted to save them (or their contents) elsewhere, so it took a bit of time. But it's done: removed the Dropbox folder from my Mac, removed the app from my iPhone.
Deleting my account may be a problem, though, since the email associated with my account is no longer valid, so I can't get the 6-character code they send after I enter my password. No easy way to contact Dropbox about this, but I did send off a request using the one form I could find.