Although both chilli and sweet pepper plants are generally ‘grown’ as annuals here in the UK they are actually classified as ‘tender perennials’ and it is certainly possible to get second and third seasons out of the plant.
Chilli plants generally require a minimum temperature of 7 degrees centigrade. In order for you to extend your season and possibly get a second season out of them you will need to move your plant into a heated greenhouse or into the house. The plant will need to sit somewhere that it can get as much natural light as possible. A sunny kitchen windowsill or a conservatory are both perfect locations. Although you can control the temperature by moving the plant indoors it is sometimes impossible to counteract the extremely small amounts of daylight we get during the very short days in the dead of winter. Chilli plants may very well go into a dormant state. They often lose their leaves and some of their stems will dry up. The plant may appear dead. Remove all remaining chillies in late December. Water the plant less frequently, about once a week. In the new year, if the plant has made it, as the days begin getting longer you will see new growth starting low on the main stem. Cut the old dead stems back to where you see some green. It is a good idea to re-pot the plant into a larger pot with some fresh, multi-purpose compost. Alternatively, feed the plant with a little Miracle Grow.