I'm 2-for-2 with Euro Tech. You make an appointment, they keep it, they work on your car right then, get it back to you when they are done working on it. They do top-notch diagnosis work, even if it's clear I'm going to go do anything less than a valley pan gasket on my own. They've done a great job diagnosing electrical components like sensors and control modules in particular. Physically pointing out to me the actual sensor or part that needs replaced has been a nice touch. And supplying me an old, ahem, vintage bimmer for a loaner is pragmatic and effective.
For a frame of reference, I have used Paddock and found them to do decent diagnosis, but are quick to insist on the most expensive possible way to fix your car. I definitely felt they aren't at all happy to see me entertain less expensive options. Oh, and even though I had an appointment, they held my car hostage for a week to read computer codes and diagnose a failed emissions test due to bad cat converters. With no loaner. [Lesson learned, I bought an OBD reader the next week!]
Euro Tech is flexible, does solid diagnosis work, and is great for many types of customers.