We still need to be cautious because these are studies and not conclusive, that is not written in stainless steel. The Weale, Weiss study of 2002 was interesting, suggesting a possible mass migration of much more than 50%.
"We note, however, that our data do not allow us to distinguish an event that simply added to the indigenous Central English male gene pool from one where indigenous males were displaced elsewhere or one where indigenous males were reduced in number." It still leaves therefore 3 possible models open. Each one needs to be interrogated.
"We estimate the proportion of Saxon ancestry in C./S England as very likely to be under 50%, and most likely in the range 10% ‐ 40%." The point about this is that is across the entire genome. If an anglo saxon male had a son with a british female, the son looks 100% anglo saxon if you look at the male specific part. If you look at all of it, it is 50:50.
Anyway, in my opinion the invasion/migration of Germanic peoples from the continent had to be large enough to cause the native population, whatever their number, not only to change their language, but also their religion and culture.