Since you say your mare has a sensitive back, Black Country saddles often come with serge panels which are felted wool instead of leather. They are very soft, light and breathable, and IME, horses love them. Only problem is that BC saddles tend towards the wider side and are often built on hoop trees.
Black Country and Frank Baines both make lovely saddles on a variety of spring-steel trees with pure wool flocking. Both offer the option of serge panels. I generally have a few clients stalking eBay for used at any given time, and I can tell you that if a used Black Country comes up at a reasonable price it generally sells fast! It can be a challenge determining whether a Black Country Saddle is on a Classic or Freedom (hoop) tree. Some of the older Frank Baines saddles are designed differently even with the same name, so that can make them a little challenging.
Sizing is very different from one brand to the next! If you want to send tracings I can measure them and advise on size.
I have a baines and love it. IMO they run on a wide side for trees. Kent and masters is a great value, and uses gullet bars you can switch out.
its mostly about trying and seeing what works. If you can go to a tack store with a large consignment inventory you can try a bunch.
Many of the UK made saddles can have serge panels and many of them hold their value quite well. Most QH I fit are candidates for hoop tree or laterally broad type trees, sometimes needing panel support. Black Country, Adam Ellis, Baines Capriole Extra or Balance, Detente, are just some that offer broad trees and are flocked. It really boils down to what your horse needs that will also work for you and then you can search for the best value.
I have an older Custom. I got it for $800. It fits my horse and me perfectly. MY horse his Mr. sensitive. I would determine if your horse needs flatter panels or curvy panels. That would narrow down the choices. My daughter got a Kent and Masters jump saddle and he loves it. They make a dressage saddle on the same tree. It has exchangeable gullet and knee blocks you can move. New they are about 1700… a midrange saddle. Not the top quality but still good.
A saddle fitter custom ordered a Black Country for my horse. The only problem was that even though the demo saddle fit me just fine, the custom saddle that fit my horse perfectly did not fit me perfectly (I have hideously long femurs). Sitting in it was comfortable, but actually riding in it was not. Make sure your fitter evaluates the fit as you ride in all three gaits. When I was putting my younger horse under saddle I opted for a Thorowgood because I knew he was still growing and his shape would change. It’s not fancy, but it fits him, it fits me, it is adjustable and it is wool flocked. I also don’t worry about riding in the rain!!
