To answer your questions, Tony, RT side-effects are cumulative and usually peak about 10-14 days after treatment ends. I had 32 sessions of RT, so six and a half weeks, Monday-Friday.
The first three weeks or so I was absolutely fine. I then started to have difficulty peeing, which is very common - the radiation makes the prostate swell. I was prescribed Tamsulosin which completely sorted that out.
Towards the end of treatment I started passing large amounts of green slime from the rear end. This again is common: radiation irritates the bowel and makes it produce more of the mucus which lubricates things. Frequent and loose bowel motions in general. Also an increased urgency to pee (again, radiation irritates the bladder) until I was having to "go" every 40m or so, 24h a day, which was exhausting. I bought a urine bottle (Amazon) which was a big help. You get back to sleep much faster if you don't have to get out of bed.
Finished treatment. Side-effects reached their worst about 10 days later. Peeing frequently rapidly subsided. Back to normal within a few weeks. Bowel issues took much longer. At least three months to start stabilising and probably a year to return to any sort of normality. If I went out for the day I took at Imodium tablet. It didn't disrupt my life.
I'm probably making it sound worse than it was! It really wasn't too disruptive and I managed fine. I'm now three and a half years after RT. I'm still on Tamsulosin and will be for life, but no issues. Bowel is different to before, but not troublesome.
Hope that's of some help to you,
Chris