There have been Chinese take out shops in my town for as long as I can remember. But none of them deliver. Few of the bigger joints like Chinese Dragon and Flower drum deliver but since they are a bit out of town it takes longer to deliver and they have some minimal amounts they will send.
So why don’t the little shops deliver? All it takes is a guy on a motorbike or 3 wheeler. If you can’t keep your own delivery guy just talk to a few guys in the local 3 wheeler stand and get it going.
In this age of copy paste business models you have to stay ahead of the other guy. Besides I really don’t want to drive up to the take out place today. 
Update: Jade Maharagama delivers! 2839839
I’ve always thought that a good business idea for Colombo would be a home delivery service for anything. Basically a bunch of guys with bikes/trishaws and mobile phones.
You call, tell them what you want (food, groceries, anything) and they quote you the delivery charge. If you accept the charges, they go buy the stuff and bring it to your doorstep, where you pay on delivery.
Might work?
Ya just might work. No one really wants to try out a new idea. But if one guy pulls it off it’ll be copied all over. Do you want to do be that guy who starts it?