This group of plants will survive happily in constant lower temperatures of around 10C.
Examples are Plectranthus, bougainvillea, citrus, Clivia and Stephanotis, all of which should only be watered sparingly.
Slightly tender plants
Many plants can survive without heat as long as they are protected from frost.
Tender Salvia and Echium fall within this category, as do many southern hemisphere plants such as Grevillea and bottlebrush.
They will do well if given minimum temperatures of between 5-7C which will also suit succulents such as Echeveria and agave. Similarly, bulbous plants such as tender Nerines and Freesia, provided they are kept unwatered as well as frost free.
Palms, tree ferns and bananas also need protection from frost and can survive if given these lower temperatures over winter.