I took this picture a couple of years ago at Kew where by the Princess of Wales conservatory there is a planting of succulents including cacti. It looks quite bizarre next to the pond. It used to have more hardy plants in but had been replanted. Some here such as Aeonium arboreum 'Schwarzkopf' are totally tender and therefor are simple bedding. Others may be hardy if they stay dry enough in the winter which is a real problem in London even for Kew.