The French Ministry of the Interior estimated clandestine immigrants ("sans-papiers ") in France numbered anywhere between 200,000 and 400,000, also expecting between 80,000 and 100,000 people to enter the country illegally each year.
http://www1.rfi.fr/actufr/articles/076/article_43041.asp
Frankly, a few thousand at the channel ports are the least of their problems - especially since they are trying to leave!