The unnamed Kingsman prequel is getting put together as we speak and currently three names are being discussed for the film; namely Rhys Ifans, Daniel Brühl and Charles Dance.  Ifrans played Doctor Connors in the Amazing Spider-Man film, Brühl played Baron Zemo in Captain America: Civil War, and Dance was Tywin Lannister on Game of Thrones. 

Apparently Ifans is going to play the villain, a Russian mystic as described by the initial reports.  Brühl and Dance’s roles are unknown but are rumored to be members of the Kingsman from the time period that the film is set in.  Apparently Matthew Goode, who played Ozymandias in Watchmen, is also up for a role.