Here I start creating a map of locations to visit related to Hitchhiker's Guide to the Galaxy.
51.536, -0.104 Islington — In the novel, this is the place where Arthur Dent meets Trillian (as Tricia McMillan) during a party in a flat. - Wikipedia 
51.518106, -0.089904 Moorfields Junction (junction of Moorfields & Moor Place, London EC2) — In the 2005 film adaptation a scene shows the population panic at the demolition of Earth. - Medium article
Hitchhiker Locations