Essentially, you should do whatever the BCO/AI deems necessary in order to satisfy the Building Regulations. This should, in turn, satisfy the insurers. I grew up in a house that didn't comply with guidance in respect of these points, but the District Surveyor (as was) was satisfied that the provision of smoke alarms would be adequate, without additional measures. But times change; your circumstances may be different; your BCO/AI may take a different view.