My parents are teachers and both tutor privately too, and trust me as long as you're more than competent at the qualification you're tutoring for, then there won't be a problem, so you can tutor for GCSE no problem, although I'm not sure about A Level, it depends what grade you got etc. There is a huge advantage to employing a student as a tutor as they have been through the system so recently that they'll know how it works, whereas a French native could teach the language, but not be able to tailor it to the course. You're a bit late for this school year though.