Dear Lorraine,
If you teacher didn't request any specifics for your presentation, just sports in general, you can focus on a specific sport event. For example, you can talk about the 2012 Olympics in UK.
Or if you are looking for an overview of sports in UK, you can check out "projectbritain" website , go into the sport section on the website. There is some of the interesting information, for example, 'Netball' is popular in UK (and it is predominantly a female sport), 'Rowing' is a competitive water sport in UK and there is a popular yearly race on the Thames between Oxford and Cambridge Universities. There is also a section on 'Rounders' which is kind of like British baseball.
Best of luck!