There was a guy on my course 11 years ago who decided he wasn't going to use the question bank on principle and, lo and behold, got the lowest score out of everyone.
The bottom line is this. You have to do everything you can to maximise your chances of getting a job at the end of the course. A righteous sense of moral superiority is not going to repay your training loan, or buy you a house, or pay for your childcare. This is the real world.
Use the question bank and don't feel bad about it. If the CAA gave a
they would do something to shut it down. But they don't, and neither should you because a large proportion of the material is information that is going to be useless to you and will be quickly forgotten.
Keep your head down, do what you have to do to pass with a clean sheet. There are no extra marks for being a goody two-shoes.