Sam im sure a N1 rad is the same thickness as a GTI one, the fan shroud and connectors are different though ill double check tomorrow. Possibly a GA16DE rad got fitted at some stage.
your brave without an axle stand.. tut tut tut
It leaked from just next to the Rad filler cap on one of the weld lines. I never noticed it until I ran the car up to operating temp to test if the fans would kick in and noticed steam coming from under the bonnet. It was only a pin sized hole but I sent it back.
If I can't fix the new one i'm gonna refit my standard Autech rad.
If what you say about welding is right, I don't fancy my chances with it.