Kent

Kent was a county that Ben Jackson and the Seventh Doctor both described as "the garden of England." (AUDIO: The Mouthless Dead; PROSE: Transit) Smithwood Manor (the Doctor's house) on Allen Road was in Kent, as was the Pinehill Crest Hotel. (PROSE: Verdigris, AUDIO: The Shadow of the Scourge)

History
In 1895, Lord Jack Corrigan resided in Kent. (AUDIO: Destination: Nerva)

Another group of Daleks, who crashed after their ship's systems were damaged, hid underwater in Kent while they were on a mission called the Dalek Project. (COMIC: The Dalek Project)

In November 1920, the Second Doctor, Ben, Polly Wright and Jamie McCrimmon visited Kent. (AUDIO: The Mouthless Dead)

John and Anne Hartman lived in Kent. After John's death in 2003, Anne moved to Kensington. (AUDIO: The Rockery)

Canticum was the equivalent of Kent in Pete's World. (PROSE: The Turning of the Tide)

A group of Daleks once landed in Kent as an advance guard for an invasion. They were thwarted by a mole. (PROSE: The Small Defender)

Starship UK had a Kent tower. (TV: The Beast Below)

Behind the scenes

 * Kent was used as a filming location for Doctor Who television stories, among others, Inferno, The Curse of Fenric and notably the Dungeness nuclear power station in The Claws of Axos.

Information from invalid sources
The UNIT Liaison was located in Maidstone Barracks, Kent, ME16. The 4th annual conference on Threat Containment and Response was held there, and it was announced on the UNIT website. (NOTVALID: UNIT Conferences)