Last year before my mot was due i did loads of work on my Mondeo . New bottom arms /trackrod ends/discs/pads /front drop links/ and rear subframe bushes  . I spent 2 solid 12 hr days lying on my back in -10 temps doing the dam thing so just wanted the quickest/easiest and cheapest mot . and that was quick fit at the time (fast fit) 
Now given i do most of the work on my car myself and do the family's stuff and my step son works in a parts department i have a good idea about most bits and bobs so was rather dismayed when it failed . 
2 items it failed on . front drop link was loose (i had not done it up properly) and read droplink was abit worn ( i never swapped these and they were ok in my eyes ) and an advisory on the rear subframe bushes i had replaced (no idea why ) 
They refused to give me a spanner to tighten the drop link or tighten for me . so i then had 2 hrs to fix the issues and get back for my free re mot test .
The did offer to do the rear droplink for me for £139 (very kind of them ) 
£11 later and new rear droplink replaced and front tightened it passed the mot . Now fair enough they were both faults (neither unsafe  ) but my issue was while waiting for my mot and as i watched the various people come in and out and the quotes people were getting . 
Some woman brought in her micra which failed on the passenger track rod end . the quote ?  £179 and to be safe we recommend doing the pair !!  Over £300 for £16 worth of parts and maybe 30 mins worth of work  . 
The other eyeball popping one was a focus 2006 and a bill of over £1000 for front/rear disks and pads . Now given i had just done mine and a cost of under £100 for all parts its daylight robbery (and im in the wrong job 

  )