Issues involving decorating?

I moved into my rented property 6 months ago (there was a couple of damp patches on the walls in the lounge and in the master bedroom on the chimney breast). After a couple of months i noticed mould spores on the walls in the bedroom which have spread all over the ceiling, the landlord got some extra fans fitted upstairs and one in the kitchen(their explanation for the mould was that i do to much washing? i do 1-2 washes a week because there is only me living there), the thing is i dont know if they have worked because the mould hasn't been removed which led me to ask the estate agents about getting someone in to remove it or redecorate, they have turned round and said if i want it removing to do it myself or if i want it decorating i will have to put some money towards it. Can they actually demand money off me for it and will i still get my deposit back if i move out and leave it in the state it is in? thanks