I remember seeing a movie when I was eight or nine, where two young boys do something, and one of them is then kidnapped by a guy in a Mk2 Ford Transit and forced to work at a circus. They escape in a hot air balloon, much to the annoyance of the pilot, and somehow retrieve a stolen diamond known as the "Green Grimaldi" (the name of the diamond is my only clue to the movie)

And there was also a rowboat which was called "Titanic II"