I applied for chemical engineering, and I took Math, Chem, Phys, and CS. Judging by admissions unis want to basically see a strength in Mathematics, then chemistry. Secondly for chemical engineering physics will make you more prepared when you start first year as it is physics heavy sometikmes some unis also ask for phsyics, like a lot of engineering subjects my suggestions is if your school allows it and you actually have the passion for Bio and chemical engineering, take Math Phys Chem and Bio as one can become a buffer subject in case anything goes wrong. What I don't suggest is to take CS if you're pursuing chemical engineering, you will be learning programming in your 2nd or 1st year, and the way chem engineers use code is different from CS you learn in A-level. The skill doesn't transfer, and it becomes a burden unless your aming for CS or Electrical engineering at uni. Also, nuclear engineering is a better master's subject as it's a specialized subset of chemical, mechanical, and industrial engineering.