190 front brake judder + driver side pads worn uneven.

[gassed transit]

just changed front discs due to brake judder and passenger side looked mint (only covered 1000 miles) but drivers side was a right mess with same mileage, when i checked there was obvious run out on drivers disc + pads looked like someone had used a grinder on about 30% of pad surface resulting in a shallow angle leaving the remainder flat. both pads were like this with outside one being worst affected. is this a result of only one piston pushing out??. it seems that its pushing only one end of pads and allowing the whole thing to twist which gives the strange shanfering on pads im seeing. i may be totally wrong but new ones feel exactly the same (pulseing pedal). both pistons pushed back easily so im going to bleed drivers side caliper incase it has air trapped but any advice will be welcome.
before anyone suggests it my mate already mentioned a can of petrol and box of matches as a cure.

[MrCoffee]

If you've replaced discs and pads and it still judders, could be a warped drum. Clamp off a flexi pipe to one of the rear wheels and give it a short run on a safe road (remembering the brakes will be less effective). If the judder is still there, try clamping the other side. When the judder stops, you've found the problem side.