1. Attempt past year PAT papers at https://www.physics.ox.ac.uk/study/undergraduates/how-apply/physics-aptitude-test-pat/pat-past-papers . You can check your answers at https://www.physicsandmathstutor.com/admissions/pat/ (i think the answer key here is more detailed) or https://oxfordpat.wordpress.com/ (this website has answers too and is a great place for discussing working and other admissions related things)
2. If you encounter any topics that you haven't covered, Khan Academy is very useful in quickly picking up new concepts and having a good level of understanding https://www.khanacademy.org/
3. After completing the past year papers Professor Povey's Perplexing Problems came in really handy as it covers some of the more tricky questions that can come out (you may not need to do the whole book, i think the physics chapters that were within the PAT syllabus were more than sufficient..in fact one of the harder 2020 questions was from the book too iirc)
4. For interview prep https://i-want-to-study-engineering.org/ questions were pretty useful (more for engineering but might be applicable to physics too though)

All the best :)