Would be interesting to know what the cause of the mould was.
I had tenants in a property who were constantly complaining of mould on the bedroom ceilings and in the bathroom.
We had it cleaned, sealed and re-painted many times, only for it to reappear again.
In the end we discovered, during an unscheduled visit to the property, that the tenants were drying clothes on and in front of the radiators in the bedrooms and in the bathroom with all the windows closed, as they were out at work during the day.
This is what was causing the mould and it cost us a lot of money cleaning and painting until we discovered that it was actually the tenants who were causing it.
Not saying this is the case in the OP's property, but sometimes problems are unknowingly caused by the tenants themselves.