For France you need to permanently disable speed camera warning on your satnav. You have to carry two NF symbol breathalyser bags to France’s lower 50mg limit. You need hi-viz jerkins inside the car for every passenger. You need two warning triangles. You need all the car's original papers, including the V5C and insurance certificate. Headlights have to dip down or to the right. There must be some form of GB sticker either on the plate or separate. You need a spare bulb kit, even if it is impossible for you to fit some of the bulbs. (A new one on me is that in Portugal every car has to carry a fire extinguisher.)