For a cold garage or outbuilding, run the DD1 continuously through autumn and winter rather than switching it on and off — desiccant units are designed for steady background operation and the 300-580W power draw scales with how hard it's working, so it isn't running at full power all the time. Position it away from walls so air can circulate freely on all sides, and connect the included drain hose if there's a nearby outlet or drain, since the small 2-litre tank fills quickly at full extraction.
In a static caravan or motorhome left over winter, the DD1 is a common choice specifically because mains-powered compressor units are often unreliable once the ambient temperature drops — this is one of the situations UK buyers search for by name ("dehumidifier for caravan", "dehumidifier for garage"). Run it on a low shelf or the floor, never directly on soft furnishings, and check the tank every day or two if the hose isn't connected.
For mould and condensation on windows or in a cold spare bedroom, position the unit a short distance from the affected wall or window rather than pressed against it, and leave the door slightly open if the room is small so it can pull in air from the rest of the house. Because there's no humidistat, you'll need to judge by eye or with a separate hygrometer when the air feels dry enough to switch off, rather than relying on the unit to stop itself.
One detail worth planning around before you buy: because there's no humidistat, the DD1 won't switch itself off once a target humidity is reached the way a Meaco or Bosch compressor model will. In a space you visit only occasionally — a garage or static caravan — that means either running it on a plug-in timer, connecting the drain hose so overflow isn't a risk, or accepting that you'll need to check on it periodically rather than leaving it fully unattended for weeks.
One more practical point for a static caravan or seasonal outbuilding: because the unit relies on mains power and has no battery backup, plan for how it'll be powered if the space doesn't have a permanent electricity supply — a extension lead from the house or a caravan's own hook-up is usually the simplest solution, run via a timer if you can't check on it daily.