Thanks for all the informative and useful petrol tank advice. As the fear of whoooosh / Fooooooooom is at the back of my mind ever since my then girlfriend's Beetle developed a fuel leak 30 years ago, I'll be opting for shiny replacements made by professionals.
The other issue which has been on my mind is the door hinges. I ended up having to hack saw through the hinge pins to remove the doors, and then bought spanners on eBay to get the hinges off the doors, which turned out to be another partial success. Two of the sets of nuts unwound off the thread, one top, the bottom on the other side. Despite repeated dousings in releasing fluid, the feeling was that the nuts did not want to release their grip. At which point I removed the end of the hinge assembly with a cutting disc.
The week's other development was the tentative agreement of the body shop chap to take on the body restoration. I think he was doubtful of my ability to strip the shell, and I don't blame him, but fingers crossed that is going to take the shell off my hands and let me focus on the broken Meccano set below. So mindful of the need to get new hinge fittings, I bought a set of hinges off eBay, which should hopefully make the removal and refitting of the doors a doddle!
The issues I had getting the hinges off were a surprise, but then again, if the bolts had been there for 50 years, perhaps it's understandable. Either way, I'm genuinely buzzing at the thought of getting the body off to the hands of proper experts, leaving me with the easy oily bits.
All of which brings me to today's dumb question. Has anyone (preferably in the UK) got experience of insuring a car whilst half of it goes off to the menders? My first thought is that this is a case for a specialist broker like Adrian Flux, but if anyone has a recommendation, that would be great.