Only place in Cannes you can rent reasonably freely is Cannes Aviation, the FTO, on one of their DA40's or DA42's. All the others are "associations" a la francaise, so require you to join for the year or part thereof, so no day or week memberships, as we would be used to in the UK.
CA are highly professional outfit, although a bit bureaucratic. All their instructors are meant to speak English, quality varies a bit though.
Ask for Christian Pervieux, he's a really sound guy.
BFA