Brake failure worries

I HAVE problems with the brakes on my BA Ford Falcon. I bought it at auction nine months ago and it came with a three-month warranty. I noticed problems soon after. Sometimes the brakes would be sensitive on the pedal. The slightest push on the pedal and the brakes would work, but at other times I would have to push it further before they started to work. I could also feel severe vibrations through the steering wheel and the pedals on freeway. The mechanic I was told to take it to found an air bubble in a brake hose and released the air and the discs were machined. The brakes were good for about a week, but then the problems came back, the vibrations got worse, and a month later the brakes started to grind. This time the pads were replaced and the discs were machined again. I now have that loud noise when I brake, but I can also hear the noise when driving because the brakes aren't releasing fully and are still touching the discs. And the other day my brakes failed. The pedal was going flat to the floor. The strange thing is that after about 5km they came back to working. What can be done to fix this? Would this be from the hose problem that Ford is going through at the moment?