I'd recommend going out to a bar/club on your birthday with a mate, and taking your passport and finding a group of MILFs or a hen party. Spend some of your saved-up punting fund/cash from your parents on a bottle of champagne. Pluck up the courage to take it over to the women with some glasses and drink it with them. At some point casually show your passport to prove that it's your 18th birthday today (explain the reason you brought it was because you might not get served at the bar without it). If that's not enough to get you laid then move on to the group and keep doing so until punting fund is spent (but I expect you'll find one that shags before that).
Was it George Bernard Shaw who said that "Youth is wasted on the young"?
