When brainstorming, never reject an idea before writing it down. Most students think up plenty of ideas but they make the mistake of rejecting them before they write them down. Pretty well all ideas are boring on their own - they only become interesting when combined with others. An idea is a thought. We would certainly hope so, but if you're taking GCSE English and English Literature you may have to start out afresh with different set texts.
Persuasive writing aims to persuade.
Persuasive writing may aim to persuade a reader to change his or her mind about something, or to persuade a reader to do something. If you want to persuade someone of something, you'll need to make a persuasive case. Moreover, you'll need to do this so you don't turn your reader against you. To make a persuasive case requires supporting evidence. You can find plenty of facts and figures about practically anything from your school library, so ask your school librarian for help with research.