The photograph of Henry Albert Muggins is of Charles Laughton, the real-life husband of Elsa Lanchester.
Moabit Prison was in the Moabit district of Berlin (part of the Tiergarten Borough and now part of the Mitte borough) and was used by the Nazi government and the Gestapo for holding prisoners for both political and criminal prisoners. It was demolished in 1955. The term Moabit also refers to the Central Criminal Court of Berlin.
When 'Lord Haw Haw' refers to his inept tutor being Austrian, he glances at a portrait of Adolf Hitler who is Austrian.
"Lord Haw Haw" was a name given by the British to several different German propaganda broadcasters during the Second World War, including but not limited to William Joyce. The name is thought to have been coined by Jonah Barrington of the Daily Express. It is unlikely that the Germans ever referred to Joyce to his face as Lord Haw Haw.