In Reaney and Wilson's A Dictionary of English Surnames (3rd rev. edn. Routledge, 2005, p119) Cruys-Straete in the départemente of Nord, midway between Dunkirk and Lille in Northern France, was suggested as a possible origin of the surname.
It is clear from the large number of genetic groups in the DNA project that the surname Cruse has multiple origins. In contrast, all the Cruwyses tested to date (apart from one known illegitimate line) fall into two distinct genetic branches, each with deep roots in North Devon. It therefore seems plausible to think that the surname Cruwys has a single origin, and that the link between the surname and the Y-chromosome was broken in one of the Devon lines. It remains to be seen whether the surname Cruwys or any of the Cruse branches originated in Cruys-Straete or Creus-Anisy. In the long run I hope that more people from France will participate in DNA testing so that we might eventually know the answer.