As the series' 68 episodes span several decades of life, the cast does change and their roles do alter as well. There are many individuals who appear and disappear, but there is certainly a solid core of both staff and owners. On the downstairs side these include (but aren't necessarily limited to) Hudson, the butler (Gordon Jackson); Rose, the head house parlour maid (Jean Marsh who also co-created the series with Eileen Atkins), Mrs. Bridges, the cook (Angela Baddeley); Ruby, the kitchen maid (Jenny Tomasin); Edward, the footman (Christopher Beeny); and Daisy, under house parlor maid (Jacqueline Tong). On the upstairs side is Richard Bellamy, the head of the house (David Langton); Lady Marjorie, his wife (Rachel Gurney); James, their son (Simon Williams); Georgina Worsley, the step-daughter of Lady Marjorie's brother (Lesley-Anne Down), and Hazel, who first appears as Richard's secretary (Meg Wynn Owen). Again, there are more, and some of those listed here aren't perhaps on the show as long as one might like but they do comprise a good starting point.
Perhaps one of the reasons Upstairs, Downstairs still works so well today is that it is a period piece and as the daily life of that already set time period can't change between the early 1970s and today. Between that, the truly interesting tales, and the amazingly nonstop problems that cover the Bellamy household, the show holds up exceptionally well.
Upstairs, Downstairs is a well-scripted, well-plotted show. It is an example of great, classic, television making. What it really does is provide its audience—both the original one and anyone watching the series today—with a look at how society changed over the course of a nearly 30 year period in England. While the major events of the day are highlighted, and those unquestionably make for memorable and wonderful episodes, the show delves into any number of trends, fads, and thoughts that were espoused during the same time frame. It is brilliantly made classic television about a moment (or set of moments) in history.