Well I took it over the guy that's doing the detailing for him to have a look at it to see what the score is and the verdict is it's unsaveable!
Something has etched into the paint and badly damaged the lacquer so nothing I've done (in a way I wish it was due to something I'd done as I could at least kind of think 'oh well, my fault' and kick myself but it was something out of my control!
).
He tried a couple of times with a clay bar, DA and finally wet sanded a section of the bonnet and although with the wet sanding improving matters, it still needed another 1 or 2 gos with it and he'd already removed over 20 microns of paint thickness so it now requires the bonnet and roof repainting. Joy.
As to what's caused it, he said he had a brand new BMW M4 delivered to him that had been delivered from the dealer straight to him that had been untouched by the dealer which had 80 miles on it and that had the
same damage on it but on the boot as well (with it being a flat panel I guess). The bonnet and boot require repainting and the carbon fibre roof actually needs to be replaced due the damage and he believes it may be due to a combination of the car having no protection on the bodywork and acid rain!
I hate cars sometimes