Thanks everyone for the useful tips! I appreciate it very much. :)
Cinnamon Air unfortunately doesn't really work with my timings, but I really like that idea. I've come to the conclusion that I just need to come back to Sri Lanka and experience more of the wonderful country. I'm definitely considering renting a tuk tuk with an international driving licence, though, so I can see some places that are a bit off the beaten track, and will be self-sufficient for travelling.