As a slight aside, damp in a house is not a product of temperature directly.
It is humidity combined with temperature variation between two zones.
That is why roofs are described as hot or cold.
Poor ventilation is an example of a cause of mould followed by roofing issues/water ingress.
Not heating a house in itself does not cause mould.
Ventilation is expensive unless you use a heat exchanger.
My shower curtains get black with mould. I can prevent most of it if I throw the windows wide open, but that puts the heating bill through the roof. I used to have an extractor fan, but it ran from 7am to midnight every day and never made any difference, so I didn't bother replacing it when it kicked the bucket.
Dehumidifiers are often mentioned...do they actually draw the moisture from clothing ? Or is air movement better ?
They remove moisture from the air, and the water will evaporate from the clothes faster when the air's drier.
I still need to do more investigation - at this very moment, there's about 0.9 amps flowing that I can't account for.
Put like that it doesn't seem a lot, but assuming it's all real power that's 1892kWh PA, which is 87% of my total electricity consumption.