Heard a tale a year or so ago about a chap who flew regularly to a non-Customs airfield in France near where he had a gite. He thought it was OK.
One day the French Customs caught up with him. Arrested him, and took him to court. They examined his logbook and found dozens of entries for the same route. He was fined something like £1,000 on EACH count.
Might be apocryphal - might be true. Could certainly happen.
Not worth the risk.