I just googled "Terry saddle care" and found this from the Terry site.
What's the best way to care for the leather?
Our saddles are best cared for by washing with water and a good bar soap. Wipe it with a damp cloth and air dry it. Don't use any treatments or chemicals other than water and a bar soap. Many cleaners use petroleum that will cause the glue that holds the leather to the foam to soften and loosen. They can also cause the foam to expand and distort. Note -- if you own a Brooks saddle, DO NOT clean it with water and soap. Instead, use Brooks Proofide as recommended by the manufacturer