Hi there, I did not study through OAT, but I did have there manuals and CD, the questions are a fairly good indication of what you will see, some of the questions are in fact a lot more in depth and calculative than the real ones, but its all good preperation.
I found (and Im sure others will back me up) that Bristols online question bank is as near as you can get to the real thing and well worth a small investment of £50.
But be aware that the question banks that the CAA use are constantly having new questions added, and therefore just learning answers to questions is not really good enough, you have to know the subject in case something new does crop up, having the subject knowledge will mean you can work out the answer.
If your doing well with the feedback and sample questions you have got, then all should go well.
I am sure your instructors have told you already RTFQ and RTFA, (read the f#*$ing question, same for the answer), its easy to slip up by misreading.
Best of luck with it all.