It's the age generally known as Anglo-Saxon England (Wales, Cornwall and Yr Hen Ogledd, "the old North", were still Brittonic and Scotland was a mix of Pictish, Brittonic and Gaelic peoples.) The Viking Invasions/settlements of Great Britain and Ireland also happened in this period. That part of history in this part of the world is known in general as the 'Migration Period', the Anglo-Saxon settlement of present-day England being one of those migrations.

A Very Brief Introduction to Roman Britain

A Very Brief Introduction to The Anglo Saxons

A Very Brief Introduction to The Vikings

A Very Brief Introduction to The Normans

All Oxford University Press. Should bracket the period beginning and end (Roman and Norman) and describe the two most notable peoples/systems of the period itself, the Anglo-Saxons and the Vikings.