Also we cluster outdoor/perennials together near the house wall, beneath an over-hang if you've got one, & place eg a garden bench or table in front so that although the light's reduced somewhat, with fleece/bubble-wrap/plastic wound around the pot bases or around the whole group a few times, they're protected. Also leave a little of the surface soil around the stem exposed to permit moisture evaporation but limit water intake that then freezes & potentially damages roots. It's a compromise but each year our pot plants: hebes, roses, magnolia, jasmine, fruits, lavenders, rosemary, bay, strawbs, hydrangeas, Japanese acers, other variegated small cuttings survive. Do use unheated green-house which we stopped heating years ago because of mould problem. Brought cuttings of pelargoniums indoors & mature pelargoniums cut back,cheese plant, succulents, cacti, cyclamen, agave etc into unheated sun lounge. Hope this helps.