The only case of someone switching colleges that I encountered was where the individual in question changed subjects and had to move to a college which offered the subject they were changing to.
But to do that they had to reinterview and come back at the start of the next academic year, so it's really not something that happens without some kind of major reason. I would be very surprised if your college couldn't cater for your ensuite needs, assuming that they relate to some kind of medical condition.