According to the CAA Sri Lanka website,
Civil Aviation Authority of Sri Lanka there are two:
Asian Aviation Centre (Pvt) Ltd
Colombo Airport, Rathmalana, Sri Lanka
Tel: 94112632999, 94112635163
Fax: 94112611540
E-mail: [email protected]
web: Asian Aviation Centre (Pvt) Ltd. - Just another WordPress site
Skyline Aviation (Pvt) Ltd.
104/3, New Airport Road, Rathmalana, Sri Lanka
Tel: 94114210300, 9411911511
Fax: 94114210250
E-mail: [email protected]
Rathmalana was the original Colombo Airport and is just a few miles south of the city. There is a large GA trainng area from Colombo to the south and south-east. Check the CAA website and you will see the e-mail addresses (PPRuNe won't show them.) It will also show other details, such as licensing.
Good luck!