Hamish,

If your leather straps do become brittle, whether from age or dry cleaning, let me suggest the use of Lexol Leather Conditioner. I've been working with leather for nearly 20 years and I use nothing but Lexol to treat dry leather. Lexol also makes a great Leather Cleaner, so be sure you get the Conditioner.

Lexol is great for restoring the essential oils in leather without beinge messy or making the leather greasy. I don't think it would harm the wool of your kilts, but I would still try keep from getting it on the fabric.

If you can't find Lexol locally of from a British source, you can order it through Tandy Leather @ http://www.tandyleather.com/