I often see U.S. History broken up into two parts: pre- and post-Reconstruction (1887). Sometimes the American Revolution, or the second World War, are used as additional "dividing lines". I'm curious, is British national history similarly divided into parts? What are the events/periods that are seen as dividing lines? Why?
In as much as it is divided into periods it would be by dynasty, so one would discuss the Plantagenets, the Angevins, the Normans, the Tudors, the Stuarts, the Georgians or Hanoverians, Victorian, Edwardian, and then there is no accepted single expression at all for post Edward VII, beyond modern. There is WW1, between the wars WW2 and post-war, of course but they aren't "periods" in the way that you're suggesting.