35 demijohns sounds like you might create another problem ... but if that occurs there are other forums that can help :D
If you are going to make wines from fresh produce, then rhubarb may be your first brew, it is gorgeous and very easy, there are recipes on this board.
As for courgette wine, I have not seen this specifically, but I made some pumpkin wine recently, it is not worth doing, believe me !!! I can only guess that courgette wine could be similar, although I have heard of people doing a marrow brew that is allegedly drinkable. Not for me though.
Whatever happens, I wish you good luck and hope you become a regular contributor to this board.