This can be a b******d if you ever need to remove a bumper. Those nuts always seem to seize on, causing them to sheer. So much for galvanized steel fixings.......
(Thanks to Charlie for this little tip).
You will need to remove front bumper if you ever need to get your radiator out on a Mk3 Coupe or Convertible.
Heres the trick to get the bumpers off. Best and cleanest way to remove a bumper with seized nuts is to first of all, get a few small wood wedges. Identify which nut you are going to remove first. Pop a wooden wedge in between the bumper and body so that you can see the shaft of the big head fastener. Probably a few inches either side. Make sure you leave enough space so the you can get a hack saw blade down by the side of the shaft of the fastener. Now, using a broken hacksaw blade, saw through the shaft of the fastener. repeat for the remaining fasteners. Bumper will now come off without damaging the bodywork. You might have a scratch or two down the mating faces of the body and bumper, bit that will be hidden once they are back together. I use a air powered hack saw cutter tool for this that uses broken blades, but you can just as easy do it by hand with a good blade.
When you are in a position to put the bumper back on, fit new big head fasteners by grinding back the GRP covering the bigheads on the old fasteners. They will then drop out. Bond new ones in (preferably stainless steel ones) with epoxy resin and a bit of GRP tape over the top. Keep the shafts as short as you can, just enough to hold some nylocs and washers on. No need for long shafts. Dont bother putting the front top fastener back on nearest the badge. It doesnt seem to do anything leaving it off.