Just back from roadtrip to Cham, here's the facts if you didn't already know them:
-Calais to Cham is about 8 hours driving on clear roads going just about
-When adding up costs remember to add 120 euros for the tolls.
-Last minute ferries can be booked from Dover to Calais for about £90, however this was a five day pass, if we'd have gone longer it may have been expensive.
-We found somewhere to stay for 11 euros a night in cham, will see if i can find details of the place.
-The cremerie had plenty to occupy us punters for a few days and also looked like there was some more hard stuff there for people perhaps a little better than us.
Some photos below give an idea,
http://www.lancs.ac.uk/~balmerm/4.jpg
http://www.lancs.ac.uk/~balmerm/6.jpg
http://www.lancs.ac.uk/~balmerm/7.jpg
Go do it!