If we're going that way we usually stay on the service area near St Hilaire Cottes - which is perhaps not far south enough for you. It's a good place to say, with not too much traffic noise, dedicated caravan area, good showers for the morning (free - on asking for the key at the cashier desk) and good coffees to set you up for the morning!
You'll get lots of posts saying not to stay on service areas, but we've stayed here many times with no problems. We now tend to go the other way (Abbeville/Rouen) to by-pass Paris and stay at Aire de la Baie de Somme which is good - and has an even better caravan area, with private 'pitches' in bays, picnic tables, and rubbish bins!