Could do something depending on organisation structure, will of the team and the amount of b*lls you all have!
First thing I would do is see who will support you in addressing the situation head-on. By this I mean lodging a formal grievance, in writing, signed by as many involved parties as have the will to do so. I'm guessing that there is no formal grievance procedure, so I would just ask to have a meeting privately with the CFI and present him politely with the letter, which should set out the team's issues, illustrated with dated examples if possible.
Your offer should be either that he stops his offending behaviour, or you will take the letter to his boss (I'm presuming he isn't top of the tree). It would be worth stressing that this is your only problem and that if he stops doing this thing, all will be OK. No use pushing him into a corner I think.
If he listens and stops - problem solved. If he doesn't, see his boss. Again, present everything in writing and this time inform the boss that his CFI's behaviour may cause one or more of you to resign and pursue a claim for harrassment or even constructive dismissal (though the latter could be harder to win). Your employer has a legal duty of care to protect you from harrassment and compensation is unlimited, so he should listen!
Before kicking all this off, worth getting some more legal advice (I only have basic employment law training) - Citizens Advice Bureau, BALPA or another union may help here.
I wish you good luck - bad managers should be ousted, wherever they are
This leaflet from ACAS may clarify things further:
http://www.acas.org.uk/index.aspx?articleid=797