When I was at the GCSE stage I planned on doing Comp Sci. However, after various jobs I decided that the life wasn't for me, so I looked towards other degrees. I was one of the top at Maths in my year, so it followed that I'd do something in Maths and I started to really enjoy the more complex things such as calculus.
I looked at doing a Maths, Physics or Engineering degree. I went on a Headstart course at the end of my L6th year (year 12, I think) and really did enjoy the stuff I was taught and the project. However, when it came down to choosing what field of Engineering I wanted to do I thought about what I enjoyed. I am fascinated by the way in which things flys, and fluid mechanics. Aeronautics seemed like the best field for me to pursue my interests, and here I am.
I have examined other possibilities through my first year - such as switching to a Maths degree. However, after the whole year had finished I realised that I don't regret choosing my degree. It's difficult, but I enjoy it which is what mattered to me.