Hi Loose rivets,
Well done on going to your GP. Even if it is prostate related I still highly recommend having a colonoscopy if you haven't had one in the past few years. The worst part for me was going without solid food for near on 2 days, however it is a very worthwhile procedure as bowel cancer - which appears fairly common these days, is a largely avoidable disease.
For info, I had mine under sedation rather than a GA. In other words they put you to sleep for it and I noted that I was only out for about 20 mins.
I am going to start a thread when I get 5 minutes, on the role of the GP in our overall health as I personally see plenty of opportunity for improvement, but more on that there.
Good luck in any case.
VH-MLE