Hi, sorry to read about your predicament.
If you had been going there and developing your photos at this shop for so long, you would have known the boss for quite some time, right? sure can sit down and talk properly to reach a settlement, right? Its always important to go to your regular and reliable photo processing shop and get to know the people who do your processing. Processing is at least as important as the photo taking, cause it can ruin the image you wanted to take in the first place.
I go to my regular Kodak Express in my neighbourhood Yishun for the past 5 years, since I started with film for my travel. The owner of this shop is friendly and is willing to do post adjustment for his clients, and mind you he is very busy, and has opened up another shop in Sembawang, since I first started to go to him. He has a large client base, because he is friendly and his service is good. All my photos turned out much better than I expected.
As an example, I went to Nepal in Oct 03, and I shot a series of various exposure of the sunrise of the fishtail peak. When I send it for developing, I forgot to tell the owner not to do any post processing. In the end, all the series of the sunrise came out the same, and mind you, there were about >10shots of that sunrise, and I had more than 15 rolls of film to develop. In the end, I went back to him, apologised for not telling him not to post processed, and explained the situation. He redeveloped the series for me and did not charge me a single cent more. We have a great relationship.
As you are a professional, you need reliable photo processing labs, and a good working relationship with the regular lab you go to, so that everything can be settled in an amiable way.
A neighbourhood lab can also do wonderful job. It depends on the person developing the photos. No need for professional lab, neighbourhood labs are also professional labs too.
In this case, do what you deemed best for your customer. get a good photoprocessing lab and build your working relationship, so that your work will be more enjoyable.