Poisson - there is an article in yesterdays La Manche Libre all about a raid on a British Builder who was employing Eastern European Labour - the whole set up completely dodgy - the polish guys content to work 6 days a week - completely alien to the French that work ethic - but the book has been thrown and heavy door & keys thrown away along with big fine are all mentioned in the news article.
Do be careful.
Use local businesses - referrals are the way forward - once you have trust from someone and you are referred you're laughing - it's network city here in France. We had dreadful trouble at first - the problem being the French are very suspicious as there have been so many time wasters - once they know you are OK then you will get all your devis, people turning up on time and not letting you down no problem.
But we hate referring now - we have been let down by folk who have messed around someone we've recommended... it's a tricky one sometimes!