When most people think British Isles they think Celtic people. However for England this is not strictly true. For a start the name "England" means "land of the Angles" a Germanic tribe from Angeln in Schleswig-Holstein.
The Nordic and Germanic tribes originate from an ancient city called Asgard in eastern Europe. These tribes migrated north to Scandinavia where they settled before some moved south to Germany, and then on to England. The native Celtic people of Great Britain were forced to the fringes of England and into Scotland and Wales. The name Wales even comes from the old Germanic word "Walha" which means foreigner or stranger. The Germanic tribes which came to England were; the Angles, Saxon and Jutes.
The Angles: This tribe settled all along the eastern coasts and parts of England mainly in the north even spreading to the west in parts. Some of you may also know that there is a part of England called East Anglia, which sounds much like the home of the tribe Angeln.
The Saxons: The name of this tribe actually means "Sons of Sword" They come from what is now Lower Saxony in Germany, and much like the Angles modern day places in England are named after them. The four main settlements of the Saxons all end in the word sex and the start refers to their location, these are now Counties in the more southern near midland parts of England which are; Essex (East Saxons), Middlesex (Middle Saxons), Wessex (West Saxons) and Sussex (South Saxons)
The Jutes: The Jutes come form Jutland which is the main land part of Denmark and part of Schleswig-Holstein. This tribe is often forgotten as it does not inhabit as much of England as the Anglo-Saxons and were mainly confined to the County of Kent, the Isle of Wight and some parts of what is now London with the Saxons.
Even before the Germanic and Viking tribes were the Romans who had invaded England and Wales which was known as the Roman province of Britannia (The root of the name of the whole island Britain) It is important to note that the Romans never advance past Hadrian's wall into Scotland (then named Caledonia) and when the Roman Empire fell, the garrisons were never inforced and the Romans left in Britannia were left behind and integrated with the celtic Britons.
The Vikings also invaded England (around 800 C.E) after the Roman Empire fell and after the Anglo-Saxons arrived, they settled in Northern England and parts of the midlands and south east. The Vikings were unable to find much in the way of good farmland in Scandinavia this is why they sought to move down to Germany and across to England. They Vikings sis not just settle in England and Germany though they did manage to settle in the western fringes of Scotland and other Scottish islands, the south eastern part of Ireland and a small part of Wales. They also went to northern France too. This part of France is Normandy and the Normans invaded England at a later date in 1066 C.E. "Norman" essentially means "Norse Man" The Normans did not settle in parts of England but took the whole country and settled there (Unlike the Romans the Normans did not go into Wales)
The Norman Conquest was the last of any major invasion of England (If any invasions) and the start of the history of the English royal families with William the I from Normandy. All these people settled in England and integrated with the current populations, making England less Celtic and more Germanic. You can tell from the English language that is is both Latin and Germanic based where as the Gaelic languages of Ireland derive from Celtic roots as Ireland remained mostly Celt as the Vikings only invaded a fifth.
I figured this would be a good article to write for people from England and people with English heritage in other countries to find out more about your ancestry.