For anyone following this thread and interested in the story of the surviving Seaman from the Baron Blythswood, the following was posted on Uboat.net:
"There is a detailed description of the rescue of the sole survivor from BARON BLYTHSWOOD by U-99 in the book "Night Raider of the Atlantic" written by Terence Robertson shortly after the war (later also released with the titles "Wolf im Atlantik" and "The Golden Horseshoe".
The event is confirmed in the reports of the survivors from INVERSHANNON, who abandoned ship in three lifeboats. They observed a U-boat approaching the lifeboat in charge of the chief officer and transferring a man into it, they later found him to be the sole survivor from BARON BLYTHSWOOD who had been rescued by the Germans from a raft and given dry clothing while aboard the U-boat. However, the three lifeboats from INVERSHANNON later became separated when the weather deteriorated - the chief officer's boat and its occupants were never seen again, including the sole survivor from BARON BLYTHSWOOD.
The name of this man isn't mentioned in the survivors reports from INVERSHANNON and I couldn't find it in the German edition of Robertson's book either. Blair writes his name was Joseph Byrne, but this is not possible as the names of all casualties of this sinking are known - a sailor with this name was reported missing in September 1940: Joseph Dobson Byrne, but he had been aboard NEPTUNIAN which was sunk with all hands by U-47 on 7 September 1940."