Lost count of how many times I have seen this! Always a mistake to incorporate an old chimney into a loft conversion.
Ideally, you need to dry-line that area, so those minor dribbles don't interfere with your internal decor.
Some roaring fires will also keep the damp at bay!
I used Halfords a couple of years ago, bought the oil, used it no problem, went again a month ago, used their in-store computer, got home to find it's different from last time!
I've just bought some more oil for my Toyota Hiace van, the can looks identical to the last one, except the old one said mineral oil and this one says synthetic! anyone know why, or what the difference is?