Strangely enough my 'Other Half' is a Padi OW instructor & First Aid Instructor (in case I drown!) but I didnt want her to teach me...or the company that she works for. There's no one I trust more with my safety, so perhaps I'll hire gear & finish the dives with her after all...It sounds to me like you asked your instructors the right questions and correctly suggested things that you thought were causing problems. Given that these were your first open water dives, I think you did very well. It sounds to me like you'll be a good diver with practice. You'll also be one who questions things, researches and continues to learn.
Don't give it up, but maybe look for an instructor who is patient and listens to you. There are probably UK divers on this board who can point you in the right direction.
Still debating whether it's all worth it as I feel a bit scarred by the fact that it was.. "ok failed.. get out..." (not as harsh as that, but it felt like it....)