I have had tremendous success with finding ancestors from Pas de Calais using
Les Archives du Pas de Calais website. Going to the census pages. Was somewhat onerous to have to go through page by page but was able to find many many family members. Very delighted with the results. My Father came to Canada in 1913 and all ties with family who remained behind were gone. I have been searching and searching in an attempt to find descendants who may be in France. I believe I am getting closer!