In comparing the novel 'Lord of The Flies' by William Golding with a movie like 'Bride and Prejudice' or 'The Truman Show' I would start firstly by making some notes, and then by drafting a rough essay plan. In your notes, try recording all the times, events, descriptions and quotations from the novel that trigger the thought of the theme of 'two worlds' being present. For example, one time would be when the reader realises the boys have been in an aeroplane crash and that because the plane crashed unexpectedly in an alternative location, it has transported them into a new and unfamiliar world.
'the ground beneath them was a bank covered with sparse grass, torn everywhere by the upheavals of fallen trees, scattered with decaying coconuts and palm saplings. Behind this was the darkness of the forest proper and the open space of the scar. '
Talk about descriptions reminding the reader of their old world such as the depiction of their soiled and torn choirboy robes and comparisons with other clothing :
'Within the diamond haze of the beach something dark was fumbling along. Ralph saw it first, and watched until the intentness of his gaze drew all eyes that way. Then the creature stepped from mirage onto clear sand, and they saw that the darkness was not all shadow but mostly clothing. The creature was a party of boys'
Find quotes such as the dialogue between the boys when they talk of their past life. Now do the same for the movie. Look for examples where the characters say or do things that show the contrast between cultures, backgrounds and locations. Research the movie's background and find examples where author, director and actors brought their previous experience to bear on the content and final look and feel of the movie.Find quotes which illustrate their feelings towards each of the worlds, whether emotional, home or culturally based and apply the same analysis to the show. Then you are ready to incorporate all three into your essay plan. Make sure to have an introduction and a conclusion drawing everything together. In the middle you can divide your essay up to compare and contrast the three pieces in the light of the initial question. refer back to this question as it helps to show you are staying on track and reminds you not to include irrelevant content.