sound as if one of the filling loop valves have not shut off completely.
you should remove the metal braided hose ( should not be left connected any way) if you get water dripping out continually the valve/s need replacing.
major problems....... if you fire up the boiler the pressure will...
are you 100% sure your bathroom extractor fan is venting directly to the outside? If your ducting or connections at either the fan or the extraction point is damaged or not "air tight" you could be pumping moist air into your loft. It would be normal to instal sofit ventilators but with out...