Could be misinterpreted as an anachronism; when Robert Crawley is speaking to Mary about his grandparents being "Edwardian" he is not referring to the era that they were born but rather the lifestyle of the Edwardian Era. It was inspired by the behavior of King Edward who lived a life of lavish indulgence and required very disciplined etiquette from all around him. The rich and Aristocratic of the time mimicked his behavior. Titles could be bought by the very weathly but they were not respected by society if they could not adhere to proper etiquette. WWI changed this behavior when resources became scarce and the gravity of the new British life encouraged more relaxed rules of propriety. This conversation is a nod to how Downton Abbey changed throughout the six seasons.
Cora asks Edith, "Trouble at t'mill?" This is an old phrase of northern England referring to problems at work, ergo Cora is asking if Edith is having problems at the magazine she owns. The phrase was made famous by the "Spanish Inquisition" sketch from Monty Python's Flying Circus (1969).
Lisa Bevin, the chambermaid from Liverpool asks Lady Mary for £1,000 to not tell the story of Mary and Lord Gillingham. £1,000 in 1924/1925 is approximately £50,000 in 2024, or almost $64,000 in March 2024.