nattybumpo

The British were made up of several Celtic tribes, many of them then just recently having immigrated from the Continent at the time of the Roman invasion, which survived until well into the Germanic invasions. At that time most of them became amalgamated to each other, some of them leaving Britain (Brittania Major) for Armorica (Brittania Minor).

The British were not all simply wiped out or driven out from their former homes--their spoken language in the North of what is now England survived until around 1000 CE--and survived as separate peoples in Wales, Cornwall, and Strathclyde (the monarchs of Scotland used the title King of the Scots and Britons at least until 1286).

The modern use of the term British is a fiction invented by James VI and I.

The ancient "Hebrews" were a subgroup of the people who inhabited the Palestinian uplands and coastal Levant up through what is now Lebanon, aka Phoenicia. Basically, they were the hillbillies of the group, although much of their time was spent in the desert with their herds.