AnthonyB is right but the standards have moved on with BS9251 updated in 2014. For a residential block of flats a category 2 system is required (the categories define the design discharge density and sprinkler head coverage). The system can be fed directly from the mains, by booster pump or by tank but all this is dictated by a number of different criteria. A 9251 system may require further consultation with the authority having jurisdiction where the building is over 45 metres in height, complex, buildings with an atria, vulnerable individuals etc. On the practical side there is always resistance, particularly from those that may have to burden the cost or from those that worry about the aesthetics to their home or the cost of a faulty system if their property floods (statistically rare even with a wet system). The two most important things are the correct calculations/designs from a competent company and winning the hearts and minds of residents. Good luck.