how to improve my Cambridge engineering application

I'm currently in year 12 studying maths, further maths and physics, and am predicted A* in all three. I want to study engineering and specialize in aerospace, hopefully at Cambridge but I'm aware of how competitive it is and am slightly concerned by the fact I'm only doing 3 a levels.

My super-curriculars include: EDT gold project where im basically designing an exoskeleton for people who have no muscles so cant move themselves, did engineering work experience over summer last year, I just finished a free online course by TU Delft - An introduction to aerospace engineering - which took 8 weeks and I received a passing grade in it, I'm also currently planning a project focusing on hypersonic flight where I'll use computational fluid dynamics and thermal analysis to study how re-entry vehicles perform during re entry into the earth's atmosphere, and Im also part of an Isaac physics club at my school where we just do difficult physics questions weekly.

I've heard that Cambridge in particular look for competitions or some sort of achievement that shows an analytical mindset but I only achieved a silver in senior UKMT. what else could I do to improve my application or chances, and any advice on the admissions process (preparing for admissions test, interviews, etc) would be helpful too. Also, other than Cambridge and imperial, how competitive would this be to other Russel group unis. thanks