Every workshop has customers who are not satisfied and on the other hand, they have customers who are extremely happy with the service. Just because 95% of the people say that "x" workshop is great, doesnt mean they wont do something that YOU won't be happy with. This happens with every customer driven business.... restaurants, phone companies ...whatever!
You need to go a workshop (pick one that is close to your house for example) and if you like their work, stay with them, if you dont then try somewhere else until you find a mechanic that you are happy with.
Good luck with the new car - hope to see you on a cruise soon