Other experts have already commented on this, but I would just add that you could check with your neighbours and see if they have a similar problem. If you are living, for example, in a 1960/70’s concrete framed building and have rooms which are on the flank (side) walls, and you are living on an upper storey, then there is a risk of ‘cold bridging’ where cold un insulated walls are more likely to a place where water moisture will condense. If your neighbours suffer from similar problems, then the problem may be about the building rather than your ‘lifestyle’. But with more modern traditional construction this is harder to judge. With summer seemingly here early you could try an experiment. Clear off the old mould growth and kill off the spores with a proprietary cleaner- and see if the mould growth re appears. Keep windows open an see what happens. Your Housing Officer may be right, but if you are regularly opening windows in the kitchen and bathroom and any mechanical ventilation is working (check), then this is less likely.