RIBA and government should go further. ALL multifamily housing and places of gathering (schools, hospitals, theatres, etc) should be sprinklered. It works well in California and saves lives. If California can afford it, then the UK should definitely consider making this mandatory.
Actually, it is the confluence of several factors. Yes, building control has responsibility and its privatisation has been a negative factor. However, there is an equally important actor that must be mentioned.
The approval for combustible materials starts with the integrity of the testing agency and the robustness of the tests that they administer. The design of these tests needs to be called into question, as well as their interpretation. One of the main UK testing agencies for construction products has been BRE. It's privatisation some 20 years ago means it has less resources and is more dependent upon repeat business. One has to ask whether this has compromised their rigour and whether they have become too dependent on the supply side.