Can I terminate my lease agreement in rental property due to black mould TAS?

I've been in my rental property for 5 years. Around the second year we were there we in-counted a really bad condensation problem that has continued into this our 5th year. When reported to our rental agency we were told to ventilate the property adequately especially the bathroom, laundry area's. We open most windows in the house daily even in the winter months and always leave the window open in bathroom and laundry but the condensation still occurs daily. Around this time we discovered black mould growing up the walls of all three bedrooms it even spread to my children's toys furniture clothes and bedding all of which had to be thrown away at our expense, on walls and roof in bathroom and anything in the bathroom on the walls windows in living area and inside the kitchen cupboards. I have three children who have all had bronchitis each winter my eldest suffers from asthma and my youngest 12mth old has suffered from croup. As tenants we have run two electric heaters in the area of house were bedrooms and bathroom are, on top of the wood heater in the house. We have laid temporary carpet in hall and kids rooms as house only had Original floor boards varnished. And ventilate the house regularly all to no avail. Surely the landlord has to take responsibility for the damage the mould has occurred and to try and fix the problem. We have conveyed our black mould problem in writing to the agency over and over again for 3 years and nothing has been done. We've had enough and want out of this toxic house but are in a lease agreement til end of november. Is our problem enough cause to be able to terminate our lease agreement??? Desperate to know our rights!!!....