Not sure if somebody has got their wires crossed but the whole JAA ATPL QB was obtained under the FOIA in (IIRC) Germany and then translated into English. This was all legit.
The national versions of this QB are all slightly different, and the UK CAA has been more proactive than most in weeding out the worst of the meaningless and ambiguous rubbish. I have done the 7 IR exams this year and found very few of the really badly phrased questions which any "QB" is littered with.
But, variations notwithstanding, the various QBs on offer at/by the FTOs are easily good enough for productive revision. I used the flyingexam.com one which despite the buggy website was probably 80% "right" and that is plenty good enough because there are long runs of very similar questions, a dozen at a time, and if you learn one you can calculate any variation.
In that sense, one is actually learning by doing the QB. What more do you want? Hang upside down while studying?
Anybody with more than half a brain doesn't need to spend anywhere near 1 month on each subject. 1 week will do it nicely, full time revision.
An exception might be a foreign student who cannot speak English and his/her only way is to cheat totally. This is a huge huge issue in higher education today, in the form of plagiarism, and > 90% of postgrad material is plagiarised from the www, by foreign students who can barely read or write English.
Corruption is not relevant to this, although there are rumours that a particular school "down south" had in the past arranged exam passes, for a very fat fee.