What’s the best way to prepare for the British Informatics Olympiad?

I'm gearing up for the British Informatics Olympiad next year and would love some advice on preparation. I'm currently in Year 11 and I have a good understanding of the basics like functions, loops, recursion, and basic object-oriented programming. However, I find myself struggling with code optimization and frequently looking up syntax—like converting a multi-line string into separate lists. I've checked out some past Olympiad questions to get a feel for what to expect. The format includes problem-solving and logic-based questions, so I'm considering going through the Competitive Programmer's Handbook and tackling problems on Codeforces and Project Euler to sharpen my skills. A big focus for the competition is ensuring solutions run under one second, so I need to think about time complexity and efficiency in my designs. Does this strategy sound solid? What else should I be working on? Thanks!