Are you registered as a student group? In my old school the student groups get free use of space; all others have to pay.
At my current school we have the same problem too... we don't even have enough space for our regular lessons! The school's dance studio doesn't allow heels, so no ballroom or character shoes. And the indoor courts are in the gym, which is only open to students, but that would cause access problems for our non-student members.
Right now we just ask for big uncarpeted rooms. And even that we are only allowed 1.5hrs a week... We're starting classes next week and can only keep our fingers crossed that no one is using the room after us...
The nearest feasible studio we can do it at is half an hour's drive away... and students here have no cars