I think the lecturers already
specified that deposits cannot be taken back if u decided not to go
for the trip after u submitted ur form, unless it's the school
which decided to cancel the trip. I think this is part of the
administrative charges etc?
Well, u or ur fren can always talk to the lecturers.l Beg, cry or
what.. maybe the lecturers might even want to fork out their own
money to pay your fren. 
I'm serious, one yr ago, my lecturers wanted the response so badly
that they offered to pay for the students first if they have any
financial difficulties (per lecturer paid $100). The students then
paid the lectuerers back by instalments.