LONDON (Reuters) - Sexual antics of young British men and women on the Spanish holiday island of Ibiza could be endangering their health, doctors warned on Wednesday. Around half the 1,500 people who arrived on Ibiza without a regular sexual partner said when questioned in a poll that they had sex with at least one person during their stay. One in four young men and one in seven women had more than one sexual partner. Eleven percent of males and three percent of females said they had indulged in sex with six or more people during a typical 10-day stay...