Saw this same obnoxious scam in Italy. They hang out at metro or train ticket machines and spot someone who may be or is a tourist and proceed to interject "help" as you are using the machine. Then they want a euro, etc. for doing so.
Not being fluent in French I'm wondering if there is any standard response one can give to sho them away?
They can be un-nerving when you ate trying to concentrate on the machine and they are invading your space and sometimes even trying to operate the machine for you.