A lot easier than an English pilot getting work in France.
I live in France and have a Frozen ATPL and FI Rating with experiance, Even if I thought my French was good enough to instruct, After speaking to the DGAC they explained They recognise a JAR CPL but not a JAR FI rating issued in the UK ??
So be aware if doing a UK JAR FI course.
Most clubs dont employ instructors without the qualification, although schools who teach the rating tend to take instructors from there courses.
I would recommend contacting the school and introduce yourself to gain some contacts, you may get an idea of the market before you do the course, but would be suprised if you got a job without it.
Or do the rating at a school that may need instructors. Although be aware not all schools will tell you the whole truth.
Bon Chance !!