You can review AS maths here: Dr Frost Learning
And past papers here: OCR Maths AS-level Past Papers - PMT
Then make sure you understand the TMUA syllabus: https://uat-wp.s3.eu-west-2.amazonaws.com/wp-content/uploads/2024/05/03165619/TMUA_Content_Specification.pdf
Then read these notes: https://uat-wp.s3.eu-west-2.amazonaws.com/wp-content/uploads/2024/05/16150136/Notes_on_Logic_and_Proof_May2024.pdf
And then you can begin the past TMUA papers here: https://esat-tmua.ac.uk/tmua-preparation-materials/ alongside or after this book: Maths resources, textbooks, revision guides and workbooks | Hachette Learning
I also found this guide, which is also written by a tutor. I don’t know anything about them. How To Prepare For TMUA | A Complete Guide