Terrible workmanship

Took my car for a service to the Sunninghill workshop and they did not close the airbox properly and did not connect the vacuum pipe at all, now my turbo started to go and does not boost as it should. I phone them to inform them about the poor service I received and they said I must take my car back to them so that they can take a look them selves. I do not feel comfortable that they do anything to my car again. I am busy with the Motor Industry Ombudsman case to hopefully sort it out. They also try to take chances with parts that they say need replacing but some of it was replaced a month before my car went for the service and other parts last year. Please do not use them for any services.