I assume you are already all over Masterpiece Theatre on PBS.
Some good ones (I'm going to do without the quotation marks on the titles for now): Little Dorrit (the recent British TV/Masterpiece version, not the theatrical film!), Bleak House (the one with Gillian Anderson), the recent series Downton Abbey (I was less happy with the remake of Upstairs, Downstairs that just aired on PBS; Downton was better); the older British TV mid-80s- to 90s version of Middlemarch; The Way We Live Now (less romance, much more political and social commentary, and brilliantly done), The Barchester Chronicles (drama and romance in an English cathedral town).
The original Upstairs, Downstairs from the 1970s was great but is extremely long and does unfortunately pale somewhat visually because it's on videotape and not film, but it's a great soap opera, set in the 1910s through the 1930s, I recall.
I could go on and on. Try www.acornonline.com for British videos that might not be on Netflix though Netflix has lots of choice, I'm happy to say.
Oh! If you like a dose of historic military action, and want to get away from the long skirts and carriages for a while, the entire series of Sharpe's videos is fantastic. It follows an English soldier in the Napoleonic Wars and stars the terrific Sean Bean as Sharpe. Libraries have this series too. The first in the series, I think, is Sharpe's Rifles. My husband and I both love these.