I didn't want to say this, because of a weird sort of female solidarity instinct, but something really doesn't sit right with me at all, so I'll just say it. Women who politely say "no", are railroaded into intimacy anyway, and who then afterwards decide they liked it, are what confuse men.
One woman says "no", gets groped, and decides she liked it and it was romantic. Another woman says "no", gets groped, is traumatised, and reports it to the police (I think she would have a good case a crime had occurred). How is a man supposed to know for sure? He ought to exercise restraint of course, but I can see why it could potentially be a difficult thing to gauge for some.
Women who do this sort of thing are doing a disservice to the rest who really mean "no" when they say "no", and say "yes" when they mean "yes". Of course, the onus is not on you to correct the behaviour of others, but a little clarity and common sense goes a long way, I think.
Some honesty would prevent a lot of incidents. If you want a man who is a perfect stranger, have the guts/decisiveness to say "yes" to him. Don't say "no", then by your actions reinforce the idea that it is okay to impose intimacy after being given a "no".
Unfortunately, real life is not always Gone with the Wind, when a kiss can follow a slap, and unfortunately, not all men are Rhett Butler. Some men are unsure, or a little young, or just not really great at reading people, and conflicting signals like these can really confuse and mislead.
I am not excusing men who misread signals or are out to do serious harm, I'm just saying, let's not set up other women with difficult situations. The Frenchman may go away now thinking if even half the women he approaches in the same manner have a positive reaction to being jumped, then it is worth his while to continue such behaviour.
If the world were like a Hollywood romance, I would want to enjoy being romantic and carefree whenever possible, even with complete strangers, but in the interests of personal safety and the safety of others, I think it's unwise. The OP was lucky, in that he didn't turn out to be a complete psycho, but she wasn't to know that after 5 minutes, I dare say many serial killers and rapists in history have been known to be handsome and charming. I'm sure many young women have gone into vans quite relaxed, and perhaps even laughing.