back to disc brakes. You tried the trick of reseating the break calipers by loosening the bolts, then applying the breaklevers and tighten the bolts again?
I have cable accentuated hydraulic disc brakes on the Triban, so I can further adjust the distance between the calipers and disc rotor. I don't really have problems with the combo of prime wheels, juin tech semi-hydraulic brakes with semi-metallic sintered pads and the all metal 160mm shimano rotors without the fins.
But in the end riding in the rain makes disc breaks squeak.