Well, what happened with my friend Ben is a good example of doing it right. He is the same age as me, was in the same class at school.
Through his employer (Civil Service) he got private healthcare and that included a private annual checkup if he wanted it although he had to pay for it.
Through that Wellness Checkup they noticed his PSAs were rising year on year and that's how he was first made aware he had a problem because he had no symptoms.
It was an evolving picture over a number of years but it needn't have been cancer even then.