>What is out there that I could do that would make me excited waking up every day for the next 45 years that could also earn me enough money to cover my expenses?
At $500k, with UK tax rates (probably higher than US), you'd have $275k net. If you remove generous expenses, you have $200k a year in savings. Five years working would get you $1M.
With $1M, you would probably never have to work again (~$40k in safe withdrawal per year).
Then you'd have the ability to pick any job, irrespective of pay. Go help charities, help with research, spend all your time on open source projects, whatever you want.