There is not anywhere at the Tunnelas far asI know. We would always stop at a bonefide site anyway to beon the safe side in France especailly around that area.
We always travel out very early morning (3.30 am) and just stop for Coffee and fuel when we get to Belgium and then we stop for breakfast and another coffe stop on our way to our first site in Germany arrivingfor luch. Set up,rest abit have early supper and bed at 8 pm and then feel normal the next day. On the way home we always stop atthe Castle site at Guines just 15 or so minutes from the Tunnel. You could book in there for the night.