Ireland

Ireland was an island located due west of most parts of Great Britain. The majority was part of the Republic of Ireland, while most of the Ulster province was a separate country, namely Northern Ireland, a part of the United Kingdom.

Humans sometimes mistakenly assumed Gallifrey was a place in Ireland. (DW: The Hand of Fear, Human Nature)

In 1649, The Seventh Doctor, Ace and Hex visited Ireland during Oliver Cromwell's siege of Drogheda. (BFA: The Settling)

In the 29th century, Northern Ireland was still part of the United Kingdom. (DW: The Beast Below)

Ireland was the home of Sean (DW: The Underwater Menace), Sean Flannigan (DW: The Wheel in Space), McDermott (DW: Terror of the Autons), Alan Clark (DW: The Sea Devils), Casey (DW: The Talons of Weng-Chiang) and possibly Luke Rattigan (DW: The Sontaran Stratagem/The Poison Sky).

Chip (DW: New Earth) and Thomas Kincade Brannigan (DW: Gridlock) both had Irish accents, but neither character likely had ever been to Ireland on Earth. Their accents suggested that Irish culture survived in some form on New Earth.