Disk Brake Installation Troubles

[pixelplay]

I have bought a 901 hub motor and of course don't have the disk mounting parts because I assumed the kit would have everything with it to do this job. This really is not the main trouble though as I can order and have those parts sent to me, my main issue is that the hydraulic brake callipers that are part of my bikes standard set-up are in a position where they hit the hub motor when I try and fit the hub. I am curious how others are getting around this problem? Is there a different size disk and way of mounting the callipers that I am unaware of. It seems that load of people have mounted rear disk brakes but I can see from the images exactly how they are mounted. I really wish to keep a rear disk brake so any idea or help on this would be much appreciated. I have included some pics to help clarify my situation.