How to save up for a camera?

Okay so i'm 14 in 3 weeks and i want to save up to get myself a Nikon D5100 SLR Camera which is £519.99 and i don't know how to get money i know ill get about £150 for my birthday and i'll put £100 of that towards my camera and i would like to know some other ways to get money and i can't get a job as i'm only 13

Maybe you can ask family or friends if there's any odd jobs you can do. Have them pay you what they think is fair.