We have previously used the Black Horse Farm site when getting the ferry from Dover, but wondered if there is a site close to the Tunnel with good dog-walking (doesn't need to be off-lead but part of the walk away from a road would be nice) straight from the site.
We don't need a full facilities site as long as we have the basics plus electricity and it has decent road access.
Don't forget to leave a review of the campsites you have visited this year or last!
The closest site to the Tunnel is The Drum Inn at Stanford North which is just off junction 11 (about 4 miles from the Tunnel) - sorry I'm not sure how to link in reviews.
The road through the village is fairly quiet and looking at the map there appear to be a number of off road footpaths (we haven't used any personally).
Only one thing to take into account with this site - the slope to the camping field was quite steep last time we were there, if you have a long outfit there is a danger of grounding the rear on the way out.