Hi, has this settled down now? Did you need another vet visit in Winchester? I'm confused at the vet suggesting giant hogweed, because we have them in our wood, and inNovember and December, the plants are dead and the sun not out. Usually it needs contact with bare skin., which the nose obviously is. Maybe dead plant is just as nasty. The other thought the vet probably had was discoid lupus.
When I worked near Vicky Park many years ago, it was no go for anything after about 3pm. I hope gentrification has made it safer! If reported , the authorities will remove giant hogweed from public areas.