Apparently reptilian, the Bandrils lived on a planet near Karfel. The Bandrils' relationship with the Karfelons was sometimes friendly. The Bandrils subsisted in part on grain from Karfel. (TV: Timelash)
The Bandrils tried to invade Earth before 1997. UNIT fought them off without the Doctor's assistance. (PROSE: The Dying Days)
The Eighth Doctor and Charley Pollard once visited a Bandril spaceship. (AUDIO: Time Works)
Bernice Summerfield learned of a potential dig site on Javarda from a Bandril trader. (WC: Dead and Buried, AUDIO: Resurrecting the Past)
Bandrils attend Garundel's auction for weaponary. (AUDIO: Starlight Robbery)
Other references
The Bandrils were on the Eleventh Doctor's top five enemies list which he mentioned to the Fourth Doctor and Romana II while they were making up "top five" lists. (AUDIO: Babblesphere)
Behind the scenes
Lance Parkin has stated that the Bandril invasion reference was a joke, based on the Bandrils being "rubbish" monsters, and that "some alien invasions were beneath the Doctor’s dignity to deal with". [1]