Episode #3.3 - S3-E3
Other mistake: At the end of this episode after Edith is jilted at the altar, Albert makes some rather "home boy" comments about the food and then asks if there is any cheese to eat as if that's all he's used to or wants. This seems inconsistent since for the rest of the series Albert is the guy who seems to appreciate well-made food and wants to be a cook.
Episode #3.6 - S3-E6
Factual error: Thomas Barrow lights a cigarette with a disposable lighter which were not invented until the early 60's.
Christmas Special 2012 - S3-E9
Continuity mistake: In this episode, Cora tells Mr. Gregson that she started reading "The Sketch" when Edith began to write for him. In Season one, episode one, Carson tells William to iron "The Sketch", because "her ladyship only ever reads the Sketch."
Answer: Lord Sinderby purchased the house, furnished and appointed, from someone else, complete with staff that come with the home (some of whom aren't happy to be working for a Jewish family). He bought the title, as well. If the artwork featuring Jesus is valuable, he might keep it. Also interesting, his ancestors Anglicized their name, though he is proudly Jewish.
Michael Albert