A JOC may as well be called "a bigger, faster, hearvier a/c with different instruments to what you have been used to - orientation course. But JOC is snappier. It is perfectly reasonable for Flybe to ask that you have one to fly the Dash 8. To my knowledge there isn't a Turboprop orientation course.
You have to ask yourself why is Flybe going to pick you over any other 250hr CPL/ME/IR candidate. Showing some initiative to further your training and experience might be a good start.
Lets face it, no employer is going to turn you away for doing a JOC....