I've had excellent service from sending to Southampton directly. If you call them, they will send you out a travel case for you to package the watch to them.
Mine was a warranty return, so it was serviced and sorted within two weeks. There would be a longer wait for out of warranty work I believe.
I hate going through the boutique as you end up with a middleman that adds nothing to the process other than getting in the way if you want to find anything out. Dealing direct with the service centre is much better.