It seems that some of the first British owned mills in Germany were Shoddy (recycled wool) mills, and this was because there were import duties on woollen rags. This could be avoided if the rags were made into Shoddy in Germany.
One of the first was set up initially by a group of Batley people but within a few years, in the early 1850s, my gg-grandfather had become the owner. By 1870 he bought a mill at Kopenick which had been owned by the Blakeley family, and, probably in 1869, he established a business at Niederschoenweide. According to his obituary hundreds of Batley people were employed there until he sold the business in the 1890s.
We visited Kopenick a few years ago and got some information about that mill from the Heimatsmuseum, and were then directed to the buildings!, which were still standing, although rather decrepit. I know very little about the other mills, and am not sure exactly where the first one was; possibly Johannisthal. Stralau isn't far from here or Nieserschoeneweide, so might be relevant.
The Blakeley involved in Grunberg was a relative of the Kopenick ones, and I have a contact who would be most interested in this reference if you could get in touch privately