BA Ford Falcon brakes

About four months ago I bought a 2004 BA Ford Falcon MkII, with about 60,000 km on the clock. After about a month a shudder began to appear through the steering wheel while going around 80 km/h or higher. The shudder was a lot worse when applying the brakes. Since then I have taken the car to the mechanic on two different occasions and have had the discs machined, and later replaced altogether. I have also had the wheels balanced on two separate occasions, but nothing seems to work. The only other symptom occurs when parking, if I turn the steering wheel all the way to the left or right and move forward slowly, there is quite a violent and loud shudder that comes through the steering wheel. Some help would be great, as I haven't had much luck with my mechanic.