Ofc. Scotland did recive some German burghers if i uderstood corectly but yeah Ango-Saxon invasion was roughly newcommers who subjigated and assimilated pre-Germanic folk like local Celts and romanised folk. Naturally these people mixed + Norman conquest made sure much of vocabulary became romance. Presonally i believe Germanic element is predominant by blood. Even Germans aren’t that “pure” by blood. Indeed i believe there is no such thing as German, Slovene, etc. look.