Who should I contact?

I've recently purchased a top-floor converted flat in a Victorian terrace. The flat has three fireplaces, two of which I was told were sealed and one is working. However, when it rains one of the "sealed" ones lets in the rainwater into the fireplace. What type of tradesman do I need to contact to have a look at the problem? A roofer, builder or a chimney specialist (if such a person exists).