This community is fantastic. Thank you to all for your advice. Don't worry, I will be asking very many questions that, if it were not for the fact that there is no such thing, would be stupid ones.
I'm much more confident in what I need to do than I was earlier today. Thank you all.
Yes, ideally a rebuild on a galv chassis would be best and add more value, although detracting from originality.
It's not happening yet. I'll do that in the future and I don't mind that part of it will be redoing what I'm about to do now.
Here is my plan of attack.
I'm going to strip her down further than I really need to just so that I can see all the bits of the chassis that I need to.
I'm going to buy a welder and working from the worst bits to the best I'm going to patch the chassis. Then I'm going to hunt for thin bits of chassis that are the next points of failure and cut and plate them. I'm going to paint the whole chassis with rust preventing primer and chassis paint. Then I'm going to coat the inside with that waxy oily stuff. Whilst she is stripped I'm going to do the clutch, wheel bearings, swivel housing bearings (yes I know that she doesn't need to be stripped down for me to do those but whilst I've got the work space...) go on then... give me a list of what I should do whilst I'm there and I'll see what I can afford to do (prob not more than I've already said). There are so many things that I want to do but I don't want her off the road for years.
The next question is:-
Flux core welding without gas v MIG (MAG) welding - Discuss.