Hi Tigs,
Thanks so much for taking the time to share your story more fully and there are lots of things in it to unpack!! Also a big thank you to Tinkicker for some great input; it sounds like he is a loss to the training community.
I recently trained a lady, during my down-training phase, who was tiny, the loveliest person you could hope to meet but 5'3" and slight of build. She would tire quickly and would mentally tire too, which she attributed to being in her late 50's and never having ridden even a bicycle before. She safely completed her CBT over 5 sessions of about 3 hours each, 1-2-1 with me including her road ride (although i was obviously accompanied by our qualified instructor). While he was not happy that it was taking so long, he only charged her for 1 extra lesson; but i guess that because he didn't pay me while i was down-training this softened the blow to his picket! But even though i have been a scuba diving instructor and worked extensively with people who have physical disability as well as people of all sexes and sizes, i was surprised at how quickly that student would tire. It was a valuable lesson for me.
I'm delighted that you found better instruction and can categorically state that the DVSA is currently very focused on training standards and is actively shutting schools down (at a rate of almost 1 per week nationwide) and removing training licenses from many instructors who are not delivering safe training.
Once again really appreciate your response.