Avoid a French "emissions fine" and make sure you display the correct window sticker.
http://www.moneysavingexpert.com/news/travel/2017/03/driving-to-france-check-now-if-you-need-a-new-emissions-sticker-to-avoid-a-possible-100-fine?utm_source=MSE_Newsletter&utm_medium=email&utm_term=19-Jul-17-16788910&utm_campaign=nt-hiya&utm_content=35
This is why the UK should charge a few more pence for fuel instead of road-tax, so that all the incoming tourists can pay towards the road tax costs too. PLUS, it will make those who drive a lot of miles contribute more and those that drive less pay less.