In case anyone is interested in an update on my roller coaster ride!
I had a serious discussion with the head of the school. My feedback appears to have been welcomed, and I have switched back to the instructor that I had for the 1st 2 hours. What a difference! There is some really fundamental stuff that he made clear to me in hour 2 that was completely ignored by the other bloke, and it got lost from my brain over the subsequent >5 hours of vague fannying around. Now I can see just how useless the instruction was - there was absolutely no precision in his teaching or clear communication.
So the advice here to switch instructors was bang on, and all my self doubt and agonizing over the instincts I brought from boating was (mostly) nonsense. I just needed someone to explain to me how to fly the freaking aeroplane! Now of course I am mad at the wasted time, dosh and self-confidence. I tracked all the flights on my ipad, and looking back over the tracks it is obvious that the intensity of the work is 100x greater now, I am finding sessions demanding and enjoyable.