So I've now had a bit of time to reflect on the feedback from this morning and, TBH, it doesn't feel great.
Firstly they confirmed that the corrosion is spreading further. Not only that, but it's been repeatedly patch welded - patch on top of patch - which is news to me. He said that between those things, he couldn't even quote me on how much it'd be to sort. Instead of just cutting out bits it'd be a restoration job - something they don't do. Even if they did, it's not something I could afford.
I think the only thing left is for me to do is to see if I can find someone who either wants it for spares or thinks they can restore it. I'd only want the scrap money - I'd feel even worse than I do now knowing that it was being taken away to he crushed.
I only have the next couple of days and then I've got no option but to scrap it. I'll try and get it listed properly tonight after work but please shout if you might be interested.