so hang on, this guy said he could break the rules for you, and now that you decided you don't want the car, you want to use the rules to get your money back, and he won't play by the rules?
this may sound harsh, but if you sleep with dogs, you get fleas.
why didn't you check the s15 before you committed? why didn't you assess insurance before you paid your deposit?
sorry i have very little sympathy. the more people try to break the import rules, the more the rest of us look bad. i hope you get your money back, but i also hope you have learned some lessons from this.