So... this is how it chooses to repay me!
I opened the bonnet on the ph2 yesterday. It had been 'heavy' for a while, and I assumed it was just a lazy lifter. It wasn't though, it was a seized n/s hinge pin which decided to shear.
I got most of my ideas to fix it from another thread, but with a bit of a twist. I used an old driveshaft bolt (one of the 6 on the inner CV joint), cut down to about 15mm long or so (I didn't measure it), and with the head ground down to the bottom of the hex key slot.
After the old pin was drilled out, removing the scuttle panel gave enough room to push it through from the inside, but how to fix the outside...?
Ideally, removing the hinge bracket entirely (which I would have done if it wasn't helping to hold the door on), and making a rivet out of it with a ball-peen hammer would have been the way to go. But I decided just to tack-weld it to the bracket with the mig.
I won't tell you about the embarrassing incident when I fitted it upside down and had to do it again....