Hi Merlin!
I often visit that region: was there in Spring (so not that recent, really! LOL!)
But this isn't the greatest time to go: kind of in-between.
However (assuming you don't already know all this!) there are some good spots:
Marais de Guines (Bluethroats, Warblers etc)
Clairmarais Forest (Woodpeckers, raptors, warblers etc)
Cap Blanc/Gris Nez (Great for migration and seawatching)
Crecy Forest (Warblers / raptors / woodpeckers)
Marquenterre (White Storks / Egrets / Spoonbills / Black Woodie / migrants)
Not desperately up to date, but worth looking at:
http://www.fatbirder.com/links_geo/europe/france_nord_pas_de_calais.html
Have a great time! And Auchun at Boulogne St Martin is best for duty-free wine! LOL! And don't forget Calais Docks for Crested Larks!