It sounds like it's time to change jobs. If you don't care much about the money but want to keep learning new things and to be challenged, and would like to with on something that could have a big impact on the world, an ambitious startup should be perfect for you - if you are behind its mission of course.

London has lots of startup jobs that are likely to appeal to you. That said most people I know that lived in London did not stay long. I work in Amsterdam and this city has a lot of great and ambitious startups too, plus everyone here speaks English very well. If you're considering to move, feel free to email me. I'm sure I can help you if you're open to emigrating.