Squeeling noise when driving down the road

When I first bought my Forester it needed a lot of attention.First thing was the brakes the discs was warp could feel it under the brake pedal.I bought budget discs and pads for front and rear to get me going again.The front pad retainer clips were shagged so I threw them away and drove for a while with out them you could hear the pads on the front rattling about some times.Ive also fitted 2 new front calipers as well as my old pistons were sticking.Anyway these pads were rattling round and doing my head in so I bought some new pad retainers fitted them and and copper slipped my pads.About 2 days later you could hear a squeeling sort of noise if that's how I could describe it when the cars warm and when the cars rolling in traffic or crawling but when you press the brake pedal it stops.As you pick up speed the noise picks up abit then disappears when at speed but then it doesn't do it all the time.Im thinking out loud here and guessing but because I threw my retainers away the pads wouldn't really have bedded in properly and now the clips are there the case is the cheap pads are !Removed! and not bedding in properlyWhat do you think.Ive heard similar noises on buses and other cars