If it was paid by credit card and is more than £100, go after the credit card company.
If it wasn't paid by credit card, or is less than £100, about your only option is to go after the individual but, as has been pointed out, the practical implications of that mean it may well not be worth the hassle, and may not be successful even if it is worth the hassle. If not credit card, it's probably a case of gritting your teeth, and chalking it up to experience.