There are four squash courts at Finsbury Leisure Centre,a popular sports center in the City frequented by execs who work nearby. You can book by phone without a membership, and you're most likely to get a court if you show up to play during Londoners' regular office hours, or possibly on weekends, when courts are less busy. A 40-minute court session costs £8.10 for nonmembers,£ 6 off-peak (before 5 PM or after 7 PM). Norman St., Finsbury, EC1. 020/7253-2346. Tube: Old St.