Azaleas are hardy plants, ergo, outdoor, and require acidic soil conditions, or ericaceous compost if grown in containers. Many come in to the shops as 'indoor' plants, full of flower, at this time of year (or a little later). They will be fine kept in a cool conservatory, but indoors they are only able to take a few days in a cool room before starting to lose flowers, and then, leaves. Phil J

Southern Indicas and Belgian Indicas--the most common ones in the florist's trade--were bred for growing in greenhouses, and so may not be hardy outdoors in the colder parts of the UK, but will still do better in greenhouses, polytunnels, or bright conservatories than they would in the actual indoors. It is extremely difficult to give them enough light and humidity indoors, and they become very susceptible to certain pests, such as spider mites there. Other breeds of azaleas are hardier, and make excellent landscape plants in filtered or bright shade in the UK, as long as they get the acid they need.