Some places offer quicker courses if they theory is done beforehand!
If you believe that you are in for some surprises. The nature of a FI Course is that the theory can ony be done effectively by integrating it with the flying. You learn what to teach, how to teach, you practice it, long briefings and short briefings and then do it in the aircraft.
I can't think of any FIC instructors who would be happy to accept a student who had completed the theory elswhere. In most cases they would just do it again. The requirement for a FI Course is that you complete it at an ATO under the supervision of a Head of Traiming. There is no provision for mixing and matching bits of courses at different locations. If you did, I doubt that anyone would want to employ you afterwards.
I have seen the results of a number of cheap FI Courses over the years, to the unsuspecting candidates they were nothing more than a waste of money.