I graduated with a Physics degree from the University of Bath and had a flatmate too in second year who did chemical engineering there too. As a result, I have insight into the uni and this course. Be ready for maths. It is intense for you in your course as it was with mine. A knowledge of physics would be beneficial I believe (don't quote me on this) and in my opinion, my a levels would include physics, chemistry and maths (personally Physics was the best a level by far and maths is fairly logical maths that if you concentrate will set you up so well for uni in a science related degree). Your GCSE grades will by no means get you into university. They help with the progression into a levels but as I have said to a friend recently, they don't mean a lot in the grand scheme of things. It is now that you dictate your future (no pressure, but it's exciting!). Best of luck with it all!