Squeal when braking at slow speed - driving me mad!

[flybywire]

Since owning the car I have had an annoying squeal when breaking - usually from slow speed.  At first I thought it was from the front so replaced Rotors and pads with Pagid replacements plus using copper grease and anti squeal compound on the back of the pads - (red German spray stuff which cost a fortune).

 

 Still the squeal so off to the back to replace the rear Rotors and pads - same procedure.  The squeal still remains.   What is annoying is that I cannot pinpoint the location.  I cannot be the first to have this subaru squeal?  Has anyone any ideas before i end up replacing the drive shafts and bearings - driving me mad!  

[Adam]

The thin metal plate that sits behind the pad is designed to stop vibration and thus prevent squeel. These sometimes go missing when pads are changed and they are thrown out with the old ones.