The writing doesn't matter much at all, you just need to be able to show you've made a progression from the start to the end of your project. I usually start out collecting images from the internet and replicating them or taking small, interesting sections and painting them out. I start with a general topic sheet or two then move on to creating sheets for specific artists. After this, I find an artist I want to take influence from and begin taking photos/using photoshop, and from there on it develops into the final production. Any writing only needs to annotate the progression you've made, maybe with a small amount of artist research in the first few sheets.
As someone above has already mentioned, Pop Art is very difficult to get right and most people make the mistake of thinking it's easy to get good marks in. If you're not doing so well already, I'd seriously reconsider but if youre adamant in doing Pop Art then good luck to you!