As per post #1, he reckons a replacement bumper is £235[ish] but he'd still be in the position of finding someone to fit and spray/blend it - he's not got a garage, or the skills needed to finish a job like that to an acceptable [i.e. in the eyes of the PCP assessor at lease end] standard.
maybe try a smart repair company as its a small section so they would just blow it in on the car. I would just 'V' out the crack and bond some aluminium to the rear. non of this drilling holes and cable tie stitching etc..