Yes numbeplate was off still seems miles off, when you say fettle can you explain more?Have you taken the number plate off?
Any pictures of ur bumper up close?When the spoiler is fitted the contours around the sides arnt quite snug enough for my liking, but i have seen this problem with genuine parts also, i used a small file to fettle/scribe in so it reduces abd gaps.
Thanks for the pictures. That looks the same as mine, I tried but didnt think it would ever stretch that far, I'll have to have another go at it by the looks of it. Is the forth picture the result of you filing the curve down?You need to hook it on one side first and stretch it around to fit over the opposite side.