The edwardians is the story of an aristocratic family, in the period stated in the title. As such, there is not an obvious "plot" or storyline, rather it is a fictional account of social history and aristocratic life, and specifically how the class will maintain itself given the social change which is occuring. It's been a while since I read this, so having greatly enjoyed VSW's other works more recently, it's definitely a candidate for a re-read.
This has been published three times by Virago, with really rather wonderful cover images. Mine is the second version.