I had a issue with the flight school I used to instruct at.
Now for legal reasons I can't say to much.
However what I can say is don't be taken for a ride. The instructor market in eurpoe at the moment is in a real bad way. schools can't get instructors, there is talk of 'short-cut licence ' to teach nppl's. This is not going to happen.
Most schools take you on as self employed , they may even get you to sign a contract ( not worth the paper it is written on ) the law states that if your employer provides the main tools ( aircraft ) and the customers ( students ) then you are deemed a 'worker' as a 'worker' you have all the stat rights of an employee. i.e. holiday pay, sick pay and the likes. Check it out with a employment law firm. I was paid off not to give details so I won't.