an aside: if you want to be correct,

"Historically, the Britons (sometimes Brythons or British) were the P-Celtic speaking indigenous peoples inhabiting the island of Great Britain south of the river Forth. They were speakers of the Brythonic languages (also called P-Celtic) and shared common cultural traditions. In terms of language and culture, much of north-western Europe was mainly Celtic during this period. The inhabitants of Ireland, the Isle of Man and Dál Riata were Gaels or Gaelic Celts who spoke Goidelic languages.

A number of scholars argue that the unknown Pictish language was Brythonic, but in Sub-Roman Britain the Picts were distinguished as a separate group, as were the Gaels of Dál Riata. Therefore, the term "Briton" traditionally refers to the inhabitants of ancient Britain excluding the Picts, because many Pictish cultural traits (for example their sculpture, pottery and monuments) differ from those of the Britons and because ancient writers clearly distinguish the two peoples."

Anglo-Saxons and Normans need not apply....

However:

"Britain has been intermittently inhabited by members of the Homo genus for hundreds of thousands of years and by Homo sapiens for tens of thousands of years. DNA analysis has shown that modern man arrived in Britain before the last ice age but retreated to Southern Europe when much of Britain was ice covered, with the remainder being tundra. At this time the sea level was around 127m lower than today so that Britain was joined to Ireland and to the continent of Europe.

After the end of the last Ice Age (around 9500 years ago) Ireland became separated from Britain and later (around 6000 BC) Britain was cut off from the rest of Europe. By 12,000 BC Britain had been reoccupied, as shown by archaeology. By around 4000 BC, the island was populated by people with a Neolithic culture.[1] However, none of the pre-Roman inhabitants of Britain have any known surviving written language. No literature of pre-Roman Britain has survived, so its history, culture and way of life are known mainly through archaeological finds. Though the main evidence for the period is archaeological, there is a growing amount of genetic evidence which is still changing. There is also a little amount of linguistic evidence, from river and hill names, which is covered in the articles on Pre-Celtic and Celtic."

"The first distinct culture of the Upper Palaeolithic in Britain is what archaeologists call the Creswellian industry, with leaf-shaped points probably used as arrowheads. It produced more refined flint tools but also made use of bone, antler, shell, amber, animal teeth, and mammoth ivory. These were fashioned into tools but also jewellery and rods of uncertain purpose."

"Beaker pottery appears in England around 2475–2315 cal BC[8] along with flat axes and burial practices of inhumation. With the revised Stonehenge chronology, this is after the Sarsen Circle and trilithons were erected at Stonehenge. Believed to be of Iberian origin, (modern day Spain and Portugal), Beaker techniques brought to Britain the skill of refining metal."
"There was some debate amongst archaeologists as to whether the 'Beaker people' were a race of people who migrated to Britain en masse from the continent, or whether a prestigious Beaker cultural "package" of goods and behaviours (which eventually spread across most of western Europe) diffused to Britain's existing inhabitants through trade across tribal boundaries. Modern thinking tends towards the latter view. Alternatively, a ruling class of Beaker individuals may have made the migration and come to control the native population at some level. Genetics suggests that there was only a small infux of people to Britain at this time, around a few percent."



"There is evidence of a relatively large scale disruption of cultural patterns which some scholars think may indicate an invasion (or at least a migration) into southern Great Britain circa the 12th century BC. This disruption was felt far beyond Britain, even beyond Europe, as most of the great Near Eastern empires collapsed (or experienced severe difficulties) and the Sea Peoples harried the entire Mediterranean basin around this time. Some scholars consider that the Celtic languages arrived in Britain at this time."



So even Celts are newcomers....


By 600 BC, British society changed again. Often termed the "Celtic culture", it had by 500 BC covered most of the British Isles. The Celts were highly skilled craftsmen and produced intricately patterned gold jewellery and weapons in bronze and iron. It is disputed whether Iron Age Britons were "Celts", with numerous academics such as John Collis[9] and Simon James[10] actively opposing the idea of 'Celtic Britain', since the term was only applied at this time to a tribe in Gaul. However, placenames and tribal names from the later part of the period suggest that a Celtic language was spoken, for example the people were said to be "Pretanni". The term "Celtic" continues to be used by linguists to describe the family that includes many of the ancient languages of Western Europe and modern British languages such as Welsh without controversy.[11]



So, who is claiming to be a "native"?