Thanks for the reply Haraldur (K+), we played with a 16Fr again last weekend and this time there was a bit of an unpleasant stinging sensation which persisted for a while, but with no burning sensation after the catheter was removed. I think I will take your advise and go to an 18Fr for the next time. Indeed having moved up from a 14 to a 16, I did not feel much of a difference, so maybe I will get some of the larger sizes to play around with.
When my wife felt around for the prostate from the inside she felt the catheter tube in my urethra and it was an interesting feeling, pleasant but still not the orgasmic mind blowing sensation which I was hoping for. She may not have touched the prostate at the correct angle or with the appropriate pressure. I have to admit to having being a bit tense at the time. My wife is not a nurse and cannot describe what part of my anatomy she is touching or identify exactly what she is feeling. I think caution in this instance is not a bad thing.
She later fisted me quite deeply, and I experienced intense contractions, but with no prostate fluid or semen filling into the bag or leaking out of my urethra past the side of the catheter, so not sure if this may have been a prostate orgasm.
I have now found a 3-way 18 Fr foley to try some bladder irrigation play. I hope that the drip tubing has a suitable connection to the catheter for the saline, but we're still a bit jumpy about introducing anything into the bladder, I will read a bit more into the subject, there seems to be quite a wealth of experience in this forum.
Thanks again for your input. 😃