Crit'Air sticker for your vehicle as well? Unless your avoiding any LEZ

do not know how much they will look at a UK reg car but think they get stopped more than before as looking for cars that are there permanently, but still have UK plates these cars are normally SORN with a French CT which no one cared about too...

You don't need a breathalyser anymore but if you do have one or must be in date or you'll get a fine You do need hi vis for yourself and every passenger

Bits you most likely already have, Yellow f/vests for everyone in the car, red triangle, now in France on a 4x4 all tyres must be same mark and about the same tread level on the same axle, you need a UK sticker for the back not a GB, head light...