I don't warn others of the presence of speed cameras, because why should I defend their incompetence?
Why do we have so many speed cameras and so many collisions? Because a section of society either doesn't care about road safety, or are incompetent. Poor driving habits affect the rest of us, including, for example, reducing speed limits on rural roads because some are incapable of driving properly, in a safe and controlled manner. It's very frustrating to see really decent national speed limit roads becoming 40s and 50s to cater for the minority.
i appreciate that this is likely to be a controversial opinion, but I think there should be more speed cameras, particularly average speed cameras, more unmarked patrols and unmarked camera vans - particularly in urban areas. I think this should be 100% funded by FPN and court fine revenues. I also think that for particularly egregious offending (50% or more over a 30 limit, or dangerous driving for example) found by police patrols, it should be a vehicle seizure pending a court hearing within the following week or so. I also think that dangerous/drink/drug driving should come with an interim ban on charge pending a first hearing at court within a week or two.
Some will hate this opinion, but we're far too lenient with poor driving standards, and we all pay the price as a result.