This something I've been working on to go with my Fallout Underground idea [link]
The theme is set in london around 2290 where a number of factions are fighting for control of vaults scattered throughout the london underground.
British Republic: build out of a mix of tribes and city states in the north of Britian the faction is very much like revolutionary france.
Kingdom of the Home Counties: the Kingdom is all the remines of the United Kingdom from before the Great war of 2077, It rules the area that had been called South East England, dur to the high levels of fallout to the North the Kingdom did not grow untill the mid 22nd century.
Greater London Council: the remains of London's local government from before the war, cut off from the rest of the country it became it's own state and has ruled greater london for over 200.
Public Underground Shelters: The British government's vault project with was build into the London Underground system, unlike American's vaults most are still running.
Order of the Arthurian Knights: A group of people, who since medieval times, have waited for the return of King Arthur. But after the bombs fell 2 centuries ago they have become restless and have decided to start searching for their lost King’s tomb.