You need to be dedicated to your studies, simply learning a question bank isn't going to help you at all. There are new questions being implemented on a regular basis hence you cannot rely on just regurgitating what you have seen on a question bank when sitting an exam. Although bgsonline is a great help!
The actual content of the exams isn't rocket science, if you get your head down and learn the content you will do well.
I went with Bristol Groundschool, the course material and instructors were excellent. I actually quite miss it!