[gap]

Information on the Dick light vessel is a bit confusing:

• in the first excerpt from Les phares français pendant la Seconde Guerre mondiale quoted by you, Fichou states that the ship was sunk by the Luftwaffe on 24 May 1940. The text seems to suggest that the ship was sunk off Dunkerque, but nothing is said about her station and/or homeport.
  
  
• wrecksite.eu has a French lightship named Dyck (with the "y") in its database. Built in 1935 and sunk during an air raid on 25/05/1940 (about the same date as stated by Fichou), the ship had a tonnage of 500 grt and she was 42.5 m long by 6.25 m wide. The accompanying text states:
  
  

  Originally Posted by wrecksite.eu

  Ship based in Calais (region Nord-Pas de Calais). Was attacked by 3 German planes at 4 n. m. NE of her home port by bomb and machine gun. She sank without casualties. The crew was rescued by the patrol Joseph Marie with abother fron a minesweeper sunk during the same attack

  Information on wreck position is only accessible to wrecksite.eu's premium members.The coordinates 51°06'56N, 02°14'16E are given in a note as a possible alternative though, and they are compatible both with the attack location stated elsewhere in the same website (NE of Calais) and with the position suggested by Fichou (off Dunkirk). It is not clear if that was ship's work station too, despite the fact that she had Calais, not Dunkirk, as home port.
  
  Last, this is a picture of the ship provided by the website:
  
  
  
  
• The French Wikipedia article I had previously mentioned, under the paragraph Bateaux-feux encore visibles, mentions a Havre III lightship built as Dyck in 1935 and stationed 7 miles S of Cap de la Hève until 1981. Original text:
  
  

  Originally Posted by fr.wikipedia.org

  Le bateau-feu français Havre III (ex-Dyck), également au Havre, se visite depuis sa restauration ; il a été construit en 1935 et affecté au Havre en 1948 à 7 milles au sud du cap de la Hève jusqu'en 1981, où il a été remplacé par une bouée-phare. Il est amarré dans le bassin Vauban, devant le centre commercial des Docks Vauban, au Havre (ancien musée maritime et portuaire).

  Name and year of construction correspond to the ones reported by the previous source, but all the rest is a mismatch.
  
  
• bateaux-fecamp.fr has pictures of a "Havre III ex Dyck" light ship built in 1935 whose dimensions are given as 42.50 m by 6.65 m. This ship was apparently decommissioned in 1981 and is now used as museum ship in Le Havre's port.
  
  Ship name, year of construction and dimensions are in accordance with the ship listed in wrecksite.eu but, similar to what is reported by Wikipedia, this ship is still afloat.
  
  Recent pictures show that, if not identical, the ship currently in Le Havre is very similar to the ship of the same name sunk off Dunkirk though:
  
  
  
  
• More details on the "Havre III ex Dyck" are provided by worldlighthouses.org:
  
  

  Originally Posted by worldlighthouses.org

  
  - active lightship from 1935 until 1983 -
  
  
  Technical data
  
  Length: 42,50 m
  Beam: 6,25 m
  Draught: 4,60 m
  Displacement: 523 tons
  
  Year of construction: 1935
  Shipyard: FCM in Havre-Graville, France
  Material: steel
  Elevation: 15 m
  Range: 17 sm
  Crew: 8 men changing every 15 days
  
  History
  
  1935 commissioned
  1935-1939 Dunkerque station
  1939-1945 during WWII withdrawn and sent to La Pallice
  1949-1981 Le Havre station
  1981 sent for automation
  1981-1983 Le Havre station

  Ship name, technical data and year of commissioning are in accordance with all the previous sources, but the ship is said to have been moved for the durion of the war from Dunkirk to La Pallice (La Rochelle) and to have been sent to Le Havre in 1949. This is something not mentioned neither by worldlighthouses.org nor by wikipedia (which, on turn, states Cap de la Hève as ship's station until 1981), but it might partly be in accordance with Fichou, where he states that after the sinking of the Dick, all the other French light vessels were withdrawn from service and moved to La Rochelle.
  
  
• Last: in your second quote Fichou mentions a 1935 light vessel named Dick (with the "i", not the "y") being restored in 1945 (probably after the end of the war). He doens't say that she is the same vessel that he had reported elsewhere in the same paper as sunk in May 1940, but that's a likely assumption.

Summing up, we can conclude that:

there were two sister or nearly-sister light ships with almost identical names, both built the same year, one of them being stationed in the Calais/Dunkerque area and being sunk in May 1940, the other dispatched off cap de la Hève until the sinking of her sister, when she was withdrawn from service and sheltered in La Pallice until the end of the conflict, at which point she was restaured/modernized, renamed Havre, and re-stationed to Le Havre. This conclusion would assume several coincidences (too many to be likely). Those might explain the many contradictions between the various sources (they might have mixed up the histories of the two vessels)...

An alternative, and more realistic, explaination is that the Dick and the Dyck/Havre III are actually the same vessel, commissioned in 1935, registered in Calais, stationed off Dunkerque during the first part of the conflict, sunk in 1940 and salvaged/restored in 1945. What is curious, is that none of the sources mentioned above seems to be aware of this salvaging that might provide the trait d'union between the Dyck and the Havre III