Swim, swim, swim... If I were you, coming from the wintry of England to the nice beautiful tropical beach island of Fiji, I would spend as much time at the beach as possible. At night try to shop for souvenir, eat sea food, and sleep well! haha!
Have a wonderful time. I always like the beach. Never set foot on Fiji, though, but numerous times in Hawaii. I've been to Honolulu so many times that last time I invited my wife to Hawaii, she turned it down. And when I suggested to my sons (2) to go to with me, they said that they only go if I would get them first class seats.