
I currently study a level Biology (and also maths) as a year 12 and would be happy to answer any questions you have.
One thing which I would strongly suggest you do is to research a little more into the content of different subjects of interest to you. This can be through documentaries, online courses, webinars, articles, events etc and will help you establish whether the subject is something which truly interests you. You have until results day to figure this out and spending at least some of the summer exploring your subjects is a great idea anyway!
It might help you to hear my experience of a similar situation. During year 11 i was quite conflicted over which a levels to take. I was originally interested in physics as a field however i took an online course in astrophysics and didnt find it as interesting as id hoped because physics is very theoretical past gcse and some parts of a level. At the same time, i took a course relating to biology and absolutely loved it! This is similar to how you are unsure as to what to pursue for your studies, hence why i suggested exploring some online courses!
I applied for maths, physics and biology at the end of year 11. In the lead up to results day, i became even more set toward pursuing biology and tended away from physics (i began exploring other course options in this time). However, on results day i got a 9 in physics and it was my highest mark across the sciences so that confirmed to me that i should take it, in the same way that you getting an 8 in your mock has suggested you to take biology a level.
On starting my a levels however, i found that physics wasn’t actually a subject that held much interest for me. I love science, but the topics and structure of the a levels physics course just wasn’t something i was enjoying very much. This meant my grades suffered (although there were other reasons for this too) and I was consistently working at 2 grades lower in physics compared to my other subjects.
Apologies for the masses of information there! I hope some of it is a little helpful lol. My main point is that taking a subject for a level because you excel at it at gcse isnt always the best option. Obviously dont take subjects youre bad at but you should be pursuing subjects which genuinely spark your interest and link to what you want to spend your life doing. That will make studying easier and increase motivation so youll get higher grades with less work!
I would be more than happy to answer any questions on this or on a level biology 🙂 Best of luck with the rest of your exams!