Research is so important for capturing the authenticity of your characters, their movements, attitude, social status and even how they think, and even the background world they exist in.
I can honestly say, that watching 'TV news story' based films, I and every other current and former news camera op watch the movements of the Camera Operators in the movies, and can pick if they are just an extra, or really know what they're doing. (Loved Hank Azaria in Godzilla...Camera op in the rain, and camera behaved very realistic...water and cameras don't mix well!) Real news camera ops don't rack focus every 2 seconds to make it look as if they're 'operating' the camera.
But then, that's just a small demographic, so why bother researching or hiring a camera op to operate that fake camera. I guess it comes down to how you approach making your film and the level of detail you go to, and making it feel 'real' to the audience.
Ridley Scott goes to great lengths to do so, the amount of research combined with 'Hollywood' tweaking is a great mix. Eg. Kingdom of Heaven, the research into the arms and armour of the period of 1195 when it was set was exquisite, and then he tweaked the laws of history to bring later period style armour earlier into the century because it looked 'cool'. The average punter wouldn't know the difference, but the textures of the backgrounds, people, artefacts, utensils, and buildings create the fabric of the reality. Who cares if a helmet is 100 years too soon!
I read on a blog somewhere that mentioned 'All you see is the actors and the art department' which is so true!
My research into the SAS is based on the only information available to the public.
These three books are the best I've found so far because it deals exclusively with the Australian side of the story.