Here is another recipe, with 5 ingredients.
I like the addition of peanut butter as a binder, it may not fly in Scotland.
I think you could swap the honey for thick applesauce or use the more concentrated apple butter in this recipe without a problem. The biggest concern with adding applesauce is the moisture. You could also keep the honey and use dried apples for part of the fruit in the recipe.
5 Ingredient Granola Bars | Minimalist Baker Recipes
Have you considered using the ingredients in your favorite museli instead of the finished product? It might be cheaper and would give you more control over the sugar in the finished product.