Didoan

The Dido people were a peaceful humanoid race native to Dido.

History
When a spaceship crashed on the planet in 2493, the Dido people met with the surviving passengers, but were killed along with them by Bennett to cover up a murder he had earlier committed. At least two of the Dido people survived, and when they confronted him, he backed away in fear and fell from a rock ledge to his death. (DW: The Rescue)

Behind the scenes
The name, Dido people, is what the First Doctor directly called them in "Desperate Measures". It's possible that an grammatically logical demonym would also be Didonian.