I recommend
Accounting : Kumudu Liyanage
Business Studies : Bandara Dissanayake or Maal Wijerathne (Shakthi)
Econ: Bandara Dissanayake or Wimal Dabare (Shakthi)
Refer these threads
http://www.elakiri.com/forum/showthread.php?t=84953
http://www.elakiri.com/forum/showthread.php?t=73918