To add to Keith's post:
If you wish to appeal a question that you consider has more than one correct answer, or none, call over the invigilator and explain the problem. They will ask you to write down on scrap paper the essence of your complaint. Make it clear, and do not say anything like '...and so I went for answer (A).' , otherwise it may be rejected as a 'justification of an answer' rather than a kosher appeal. The alternative is to wait till the exam is finished, note down the question as well as you can remember it, and ask your FTO's CGI to appeal it on your behalf. We must submit appeals by cease work on the Monday after the exam, so don't delay.
When the CGIs appeal questions most copy the e-mails to the other schools for information. The CAA reply, then publish a list of the appealed questions and the results of the appeals a week or so after the results are out. We don't get anything detailed back, just something like 'TCAS question, referred back to the JAA, questionable answers'
I don't think June's M&B was unusual. Pass rates were normal.