Fly in and out of Colombo (the airport is actually in Negombo, about an hour north of Colombo).
The start and finish lines for April 2020 are currently under review but you should give a days leeway for travel either side.
All your test driving and launch antics shall be taking place HERE. It's handily within spitting distance of Colombo Airport too, and there are plenty of places to stay on the coast nearby. It's also nice and tucked away so will be the perfect spot for your test driving and partying needs.
The finish line will at Tallala Beach. It is probably around a 3-hour bus or taxi away from Colombo, so make sure you give yourself plenty of time on the 20th to get back if that's your plan.