I notice you use Particular Baptists as your sources, such as Hanserd Knollys, who nevertheless says nothing about the original General Baptists or their mode of baptism. You never go to those original Baptists, the General Baptists, who were influenced by the Mennonite practice of baptizing by pouring.
Once again, I choose to believe credible Baptist historians such as McBeth.
Oh, and this from an article on Thomas Helwys: "Helwys and twelve Baptist émigrés returned to England to speak out against religious persecution.They founded the first Baptist congregation on English soil in Spitalfields, east end of London."
You are so married to your own opinions that you cannot even objectively consider primary source materials coming from the very years of this issue. Your historians are just like you. They are so married to their own philosophical agenda they will take the word of the enemies of Baptists (some living a hundred years afterwards) than the words of the very Baptists living in 1641. You talk about bias!!!
The primary source materials make the 1641 theory complete foolisheness and yet you and your historians are so PHILOSOPHICALLY committed to your position you don't care what the actual evidence says.