You haven't said where you are in the UK, or which Abutilon you planted. Some are more tender than others, but all need a warm sheltered position preferably against a south-facing wall. It also depends on the severity of the winter as to their survival - -5 is often quoted as the lowest temp the hardiest ones can tolerate. Some people grow them in a conservatory or in a pot so that they can be taken in under glass for the colder months.