Melville's film visits De Gaulle's wartime headquarters, adding a protective wall in front of the entrance that I assume was there in 1940 and not there in 1969. Also not there in 1969 was a plaque commemorating the presence of the Free French here (placed in 1984) and one commemorating the speech made by De Gaulle from here in 1940:
Nor was there the statue of De Gaulle across the street, erected in 1993:
(These images are from the wonderful London Remembers site - 'Aiming to capture all memorials in London'.)
L'Armée des ombres visits other key sites related to the Free French in London, including De Gaulle's residence in Hampstead:
And the headquarters of Colonel Passy's secret service at 10 Duke Street, W.1:
The London Melville shows us also includes various streets in the St James's area, the Park Lane Hotel on Piccadilly, and some standard tourist sights:
And there is a trip to the Ritz cinema on Leicester Square:
For other representations of London by French filmmakers, see here.
(Thanks again, Jesse, for suggesting a London street on screen)