Just an update guys. Took the car into Audi bodyshop. They took photos and measured the paint. Paint was all original. They said they would get back to me, finally after many months Audi UK got back to me today with this:
“I have spoken with the Bodyshop Manager, who explained that the rusts found on the vehicle, including under the bonnet, aren’t perforated, therefore repair works aren’t warrantable. If the rust was due to perforation, then this would be covered under the warranty.”
looks like a dead end 🤷🏻♂️