The main cause of black spot mould in this situation is lack of ventilation and air flow but if you don’t have any windows, it can be hard to achieve a decent amount of air flow to prevent condensation buildup and the resulting black mould.
It may be that you need a slightly more powerful extractor fan to remove more of the moist air.
In terms of venting in the loft space - it should really vent externally as all you are doing is pumping the hot, moist air into the loft void and this in turn can bring its own issues.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!