Calling Fiesta owners to help me put my mind at ease!

I am the proud owner of a 2014 Ford Fiesta (mk7.5) 1.0 125 and it drives absolutely lovely. However, there is a creak from the back of it going over bumps, curbs etc. at slower speeds. I want to say from the suspension, but I honestly have no idea. Of things I have tried so far, the list is: Emptying the entire back, to eliminate items/tire inflating kit moving and making the noise. Taking the brakes apart and making sure they are in order. Changing wheels Tightening/loosening wheels Had a mechanic friend look at the springs/dampeners and suspension covers to make sure they were in order too, and not loose. Bouncing the rear, not being able to recreate it. Changing all brake pads.Have anyone here any experience with something similar, maybe even on the same type of car?It is honestly driving me nuts, and I really hope you can help! via /r/cars http://ift.tt/2sBFDfJ