I have just had my roof re-tiled and the builder has allowed unsightly stains run run down about 5 tiles from the chimney breast. He tells me this is patination oil and is normal but to me it looks a mess and on a new roof is not what I expected. I am telling him to replace the tiles but he tells me that he will have to leave at least one unpinned. Is there a better way to get rid of these stains? Will they disappear of their own accord in the near future? Am I expecting too much? Any advice would be apprecieated.