I am having a small chimney removed that served an old gas boiler (since replaced with a combi). The chimney leaks at the roof, and takes up space unnecessarily in the house. The flue currently has a flexible metal liner, but that may not have always been there. If there is soot exposed on the retained partitions, should I neutralise it, and if so, what with? Many years ago I know a plasterer who took a bucket out into the fields to collect cow dung to do this, but there are not many cows in urban Wolverhampton.