MP,
Sorry to hear of your woes! You have my sympathy. Given certain circumstances, this could have happened to many of us.
I used to instruct, firstly part time then as a full time instructor, strangely out of White Waltham. Lovely airfield and locality BUT you have to be so careful operating in and out and VIGILANT at all times!
As an instructor you are a professional pilot (whatever anyone says) and you must know both your privileges and responsibilities. Take control, be assertive and therefore be a captain! Safety and legality are the most important aspects of flying, the rest can and does follow in my book.
I learned so much as an instructor and I am now a better pilot for it. Made loads of mistakes and frightened myself to death half a dozen times! I know at my old club that I would have been tipped off by more experienced colleagues when flying with these so-called "experienced PPLs". To my mind they (but not all) are the most dangerous and the ones most likely to get you in trouble or worse! Perhaps junior/new instructors, especially the young ones should be mentored a little more.
Good luck now!