I think as others say its down to education for many cases.
A lot of people only know about the main cancers, and might not even think its possible to get cancer in other places, as I thought before diagnoses.
That being said, I think its also the fact that many people don't want to get diagnosed and will perhaps ignore any symptoms they have until they can no longer.
You also have some doctors that seem to make assumptions, perhaps because some patients are not old enough (or too young), that it cannot/or is hihgly unlikely, going to be cancer. When in fact it is. Its a difficult one, doctors must face so many people a day fearing they have cancer because of a symptom, and most of them won't, its just finding the ones that do.
I have family members who have been treated by private healthcare (not for cancer), the only difference I could notice was how long it took for treatment to begin. You have to wait longer on the NHS, but apart from that many NHS consultants also do private work, as mine do, so even if you were private you may still get the same consultant, its just how fast you get access to the treatment. Facility wise the private hospitals are nice, much like a hotel, but all that matters is the health care to me. Even if I had all the money in the world, I would have still had the same treatment.