MOH worked at a uni in Brittany a couple of years ago and had a lot of problems getting paid (he got it eventually) but french colleagues who had also worked at the same place were still chasing money a year later, even with a contract. I, also, following on from a fixed contract at a lycee, agreed to do some cramming for some students, on behalf of the lycee. I didnt chase them for a contract as they already had my details and it was only 2 weeks after the end of my fixed contract. That was last June and after a lot of chasing I received the payment last week (8 months later). They want me to do some more work in April but I will be insisting on a contract in advance.
Rates of pay don't know - depends on whether you are AE.