I have a 700 litre Ionics delivery unit fitted in a Renault Trafic.
Last winter I totally drained my system every night, I took the DI filters off and put them in home with poles & hose real, this takes about 5 minutes.
I have a static set up in my cellar, 2 loft coffin tanks holding 554 litres in each, wrapped in insulation jackets, each tank sits on 3 inches of polystyrene.
I put two 300w heaters in each tank and it kept us going upto about 3pm each day before hoses started to freeze!! that was on the coldest days.
Hope this helps!
Regards
Simon