Even if you find the skilled technician (e.g. @fatigue ), the question is whether you can get spare parts. Put the costs for spare parts and labor together (check the repair videos how many steps are required to get to the shutter) and you can easily get a newer, second hand model for the same money.
try going to P&G photographic center (https://pgcameras.co/) over at adelphi or peninsula. or camera workshop (also at peninsula). but i suspect their advice would be to replace the camera as the repair costs might be more expensive than just getting another 550D.