I was also in this difficult situation a year ago. All the ESF schools would not even accept my application because I did not live in their 'catchment area'. I had to move to the area first before I could even apply. But my argument was that I will not move to the area if you dont have a place for my kid. I will move to whichever school offers the place.
In the end I was tired of going round in circles with these ESF knuckleheads and I enrolled in AISHK (Australian school). Being Australian put me at the top of the waiting list, but even then I still had to wait about 6 months to get a spot.