I lived in France for a couple of years, I'm no expert but here are some ideas...
I used this website a couple of times:
http://www.6annonce.com/. It was a mixed bag, I prefered to stick to eastern european girls, usually they have the description in English and they do speak it to some degree. Sometimes the pics are real but quite old, sometimes are fake, it might be pricey, but for me was the best option.
Agencies: I used two east european agencies:
http://www.your-dreamed-girls.com/Escort-Paris.html
http://versailles-escort.com
Pics are real, but again, taken a few years back. The girls can usually be found on the above website as well.
Another option is
www.vivastreet.com. This is the French backpage, you can use google translate to go around and search, some of the girls speak English, but most don't. Best is to call and ask