Shoe leather upper restoration

[Blown2CV]

have managed to get a weird gum/glue like substance over the leather upper on a pair of shoes. Have removed as much as I can but in the process of doing so have made a bit of a mess of the leather, and it does appear stained by the original goo. I had returned them to Loake, but they had said they could not do a proper repair on them as their repair centre is not a full tannery. Any ideas of any good quality service which might sort this out please? thanks