It seems the French police have been cracking down lately on British drviers who aren't carrying a high visibility vest in their car, and have been handing out on the spot fines of 90Euros. Be warned though carrying the vest is not enough, and you can still be fined if you have it in the boot, it has to be in the cab, when travelling in France I make sure mine is stuffed in the glove box ready to be produced at a moments notice.

This is an example of where even though the EU has tried to bring standardisation of laws across member states, it pays to do some research before travelling, and make sure you are carrying three basic items that will cover you across most of Europe, a high visibility vest, a warning triangle, and a spare bulb kit, although you should check you breakdown cover is valid too before you travel.