Just some more thoughts, Hugo. Most of my appointments , you should be given all 20 when you first attend are around 12.00-12.30. I've had a couple early in the morning and one in the afternoon. The lunchtime ones are much better as, at least for me, it gives my system time to settle down and make sure I go in with empty bowels, gas free and full bladder. It does mean though that the whole;e day just about gets taken up with the visit.
My Trust, South Tees, has a good system. I live a relatively short distance away and I call the machine I'm due to receive treatment on about an hour before my appointment time. They can confirm whether things are running to plan and when I should drink water to fill my bladder. This works really well with much less hanging about.