I really like going to Max Sports to get my badminton racquet restrung. I also purchased my badminton racquet there. The owner and his wife work there and they answered many many questions I had when determining which racquet would fit my playing style. No pressure from them at all at any time.
Service was great. Not cheap, but not unreasonable.
So far, this is my go-to place for any badminton needs. They also sell tennis racquets. Both the owner and his wife are quite knowledgeable and helpful.