Bernard,
Here's another comment from across the pond. I'm Steve Poulos. I teach the IICRC LCT Course and I work for a Compnay called HydraMaster. We make Van Mounted Carpet Cleaning Systems. We sell ZERO products for leather.
With that out of the way, I love leather cleaning. Select your products well. Many products say they clean leather. Fewer still are for Leather Furniture. Leather covers a lot of territory. Shoes, belts, coats, gloves. Furniture however has the longest life span. Our job when entrusted with our customers goods is to do the very best, Unless your the second best of course.
Like carpet cleaning products, there are good and there are bad. Same with leather.
The type of solvents your product contains I can not say. You will find that painted (Pigmented or finished) leathers have a clear topcoat finish to protect the paint. Today, they are usually a nitrocellulose finish or water based urathane with a plasticer to keep it flexable. If your solvent attacks the top coat, the leather will look fine but may begin to feel sticky or gummy and soon show cracking in the finish (fractured).
Many contain an organic solvent from citrus and castor or Rincus oil called a condtioner. Great for boots, bad for furniture as it blocks it's moisture absorbtion rate and promots dryrot and seam failure.
You have many choices. pick well and be a success. Don't expect a manufacturer to be liable however for your actions. If you hold yourself out as a professional, it's reasonable for your customer to assume you have taken the time to learn your trade. Have a great time and keep it clean out there.
Best Regards, Steve