Hello, I am sitting the British Informatics Olympiad this year and wanted to know what I should do to practice.

I am very new to the informatics olympiads but I have a little experience with competitive programming. What resources should I use (other than past papers)? Are there any solid training routines. In particular are there any good resources for combinatorics? This is the first time I am practicing for a competition and it is the last year that I am able to sit the paper, so I don't want to waste it! Also happy to practice with anyone else, please let me know!

Thanks!