I am 19 years old and currently doing an apprenticeship at a mid sized web design company in the UK. I recognize that as a self taught programmer (I started at 16) my chances of ending up at a major company are very slim, but it's human to dream.

What I was wondering is, do the largest companies, google, apple, microsoft, etc. take people based on past work and merit, or is having attended university always a requirement? I should elaborate that as well as the web design, my company has a once per week any language hackathon where we race to create a minimum viable product or solve a difficult issue, so my experience with programming is outside of "just" web design and I study 3 nights per week in my spare time when not working on my personal projects, with both coursera and MiTx.