A new gameplay trailer for the DLC-sized mod Fallout 4: London has been released - the game should be available later this year:
More information.
Fallout London - Official Gameplay Trailer
Fallout: London is a DLC-sized mod for Bethesda's Fallout 4. As a continuation of the base game, the mod will allow the player to visit the previously unexplored post-apocalyptic environment of London.
As a divergence from previous official titles in the series, Fallout: London is not set in America. Visiting a totally new setting allows for us to explore totally new cultures which have not homogenized with their American counterparts. It also allows us to explore pre-war European history, and the effects the Resource Wars had on the class structured society of pre-war Britain.
More information.