I would maintain that a small electric heater throughout the year thermostatically controlled, would alleviate much perceived damp, all mould and particularly condensation which causes it. And keep it cosy. If my £600 Daisy May deserves it, then so does yours! I think it`s well worth the small extra cost, rather like cheap insurance. And it becomes a comfortable hideaway . . . .!
------------- Peripheral people don`t have as much excitement but they sure live longer