Hadn't noticed this thread update, but I did eventually email Nissens UK and got this response:
They look to be the same unit however are a different construction
Image 4 is a brazed unit, Image 1,2,3 are mechanical construction, however they will interchange
Nissens uk ltd
So I fitted it regardless and works all ok! Probably won't last as long as the better looking part but I needed the car back on the road. As stated, the fins are quite easy to bend/slice your arms open so be gentle!