Oxford University Press and Hodder Education often provide the first 2-3 chapters of their O Level books as free sample PDFs. These chapters usually cover Number, Algebra, and basic Graphs—perfect for starting your revision.
Search for “O Level Mathematics” on archive.org. You’ll find older editions (pre-2018) that are great for practice—just check the syllabus changes. math o level book pdf
The Ultimate Guide to O Level Math: How to Find (and Use) PDF Resources the Right Way Oxford University Press and Hodder Education often provide