Very interested to see this post.
I had a pre-cancerous polyp removed in 2009 and was told I would be given a colonoscopy every five years from then on.
When 2014 rolled around, not only was I not contacted (I had assumed that I would be on some sort of list and that when my name came up I would be contacted automatically) but when I rang the colonoscopy department, they had no record of my being due for a recall. My GP got it all sorted out, I had one, all clear, and I am due another one (deep joy) in 2019, if I'm spared.
So....five years between screenings, but you have to remind them!