In the opening scene, Edward says he's off to watch Fulham v Manchester United, and teases Hudson - "Maybe one day Chelsea will get into the First Division".
In 1908-09 Chelsea and Man Utd were both in Division One - but Fulham weren't. They'd only joined the Football League in 1907 and were still in Division Two in the 1908/09 season - they didn't make it to Division One until 1949.
It is surprising that they didn't take Sarah up the back (servants) stairs, instead of the main stairs past the drawing room.