Purchasing materials for work in France is fraught with difficulties. I now only buy something that is cheap or that I can mend if it goes wrong. Otherwise I buy from the UK and bring it back with me. For instance, with central heating I am happy to buy radiators and pipework in France, but I buy the boiler from the UK.
Bitter experience of spending many thousands of pounds has taught me that there is in fact very little consumer protection. If you return goods to a shop it will be your fault for buying it in the first place. If you go to the 'Consummateur' they will write a letter for you telling you that it is the fault of the supplier and then the supplier will still do nothing.
You should also be aware that many contracts (like insurance) must be cancelled 3 months before they expire or you will have to continue for another year. The same applies in Holland but I don't know all the categories.
Caveat emptor is the rule of the game I'm afraid!
Mike