Thanks again for all your comments, everybody has been incredibly positive (tempting fate!)... Which leads me to believe this project is worthwhile.
Interestingly, you've come up with your own question this time. So without further ado let's put it to the vote.
Should drugs be a part of this movie;
A. All the participants take hallucinogenic drugs, which starts a psychotic episode.
B. One member of the team secretly takes drugs and doesn't tell anyone else.
C. Nobody has any drugs because it might cheapen the insanity theme.
If we're dealing with sanity/insanity as a theme to completely ignore the effect that drugs can have on the mind might be misrepresentative. Personally, I think it would be a bit strange if eight students went away on a trip without any drugs. Although they are crossing from UK to France so it's possible. There's always an abundance of magic mushrooms in the woods around the old farm house.
I'll post some pictures to give you an idea of the location.
Finally, on the subject of drugs... I would like to know your thoughts about treating psychosis with antipsychotic medication and electroconvulsive therapy (ECT). Does anyone have experience researching this? If so, I would love to hear from you!