Anti freeze is probably your best bet. Insulation will help but can't be guaranteed. Don't forget the cold will come through the floor as well.
Anti freeze is a pain when you first do it but becomes a habit.
You can also run it through your hoses. You need 2 containers, 1 full of anti freeze and 1 empty. Attach your hoses to the machine and put a blank male connector on the end. Run your machine with the anti freeze in it until all the water is expelled and the blue (or red) anti freeze starts coming out the end of the hose then quickly put the end of your hose into the empty container. Once you are sure the full system is full of anti freeze switch off. Next morning its a case of first job, fill machine with water and run until all the anti freeze has gone into the second container, switch off and you are ready to start.