No matter where i move the start marker, each time i press the play button it always starts at the beginning? it didnt use to, so i dont know what i've done wrong. If i want to see a clip in the middle of the film i was editing it wont play it and jumps to the start of the film.
Regular playback starts at the position of the play cursor. The range you have enclosed between start and end marker doesn't matter here. There's a special playback function for that. You can find the "Play back range" button next to the regular play button in the transport controls or use the "#" key on your keyboard to start the range playback.