In the observation room of the explosion victim, Jack introduces himself as "Owen Harper," referring to the character played by Burn Gorman in Torchwood seasons 1 and 2.
Gwen and Rhys's Welsh cottage is called "The Old Rectory" and is owned by the British National Trust. It can be rented as a holiday cottage.
The picture of Captain Jack that Esther finds in the CIA archives, is actually a still from The Empty Child (2005) which is the episode of Doctor Who in which the character of Jack first appears.
The name for the CIA analyst, Esther Drummond, was presumably taken from the "Wester Drumlins" house from the Doctor Who episode "Blink".
This episode takes place from March 18 to March 21, 2011.