some basic checks first before you go any further imho.
Wheel bearings, jack car and hold wheel at 12 and 6 oclock, rock the wheel and check for play. If the bearing is worn then the disk wont be central, when the pads grab the wheel it sets off a judder.
Wishbone bush play, tends to give intermitent judder, so may not be your problem in this case but bushes are so often shot down to age alone it def worth checking. They do move as they are rubber, but they should be firmly held, no slop. Jack and hold the wheel at 9 and 3 oclock and get someone to press the brake. You should feel controled firm movement with some good pressure applied, not loose play. Any hard knocking can be trackrod ends to stearing arm. Also get a bar and lever the wishbone joints look for same feel.
Sticking caliper, spin the wheel when jacked and feel if the wheel spins freely, if it binds then you could well have sticking caliper sliders, these allow the caliper to centre on the disc, if they dont slide then as the pads wear one side will rub constantly, possibly warping the disc which you can also check when spinning the wheel by hand, listen for a shush shush shush noise or uneven drag when the wheel turns.
Disc not centred, or badly seated. Involves removing wheel and caliper. Then remove disc, check mating surfaces are clean with no burs or dings that prevent the disc sitting flat to the hub. Then refit the disc with the wheel bolts to centre the disc, tighten the 5 mill allen key to hold disc in place. Remove wheel bolts and refit wheel.
Hopefully with those checks you should find your problem. Hth :-)