Indigenous and modern day native British Islanders have a strong genetic link to ancient Basques (who came to the British Isles from Iberia in Southwest Europe) -
So, based on the overall genetic perspective of the British, it seems that Celts, Belgians, Angles, Jutes, Saxons, Vikings and Normans were all immigrant minorities compared with the Basque pioneers, who first ventured into the empty, chilly lands so recently vacated by the great ice sheets.
but even though my most recent European ancestors came from England, my genetic link to the ancient Basques is relatively not so great, making it unlikely that the British Isles is the indigenous home of the bulk of my own European ancestors. Instead, I seem to be genetically more related to "immigrant minorities" of the British Isles - namely, to the Celts, Belgians, Angles, Jutes, Saxons, Vikings and Normans.
My autosomal STR genetic deep ancestry test results support this, indicating that I am deeply more heavily Scandinavian (Sweden, Norway and other Fennoscandia countries), Celtic, Belgic and Germanic, with my U5b1b1 genetic motherline distinctly indigenous to arctic northern Scandinavia. My chromosome painting is also predominantly Northern European.
So, it seems clear to me that the bulk of my ancestors were likely not indigenous natives of the British Isles, but rather were native to Scandinavia and also to the Celtic-Germanic lands of continental Europe - groups who then migrated to the British Isles and subsequently admixed with the Basque-sourced native population there (as I do have some Basque genetic ancestry, but much less relative to my Scandinavian-Celtic-Germanic ancestry).