I still feel it would be better for you to save your money and stick with the gaffer tape through the winter. Clearly from what you have said, there is uncertainty in your life and if push comes to shove you would sell your vw's if need be. In my opinion it just wouldn't make financial sense to throw money at the van at this time, you may need that money soon.
Fix the roof as soon as possible, it will rot everything else out and take a few hundred pound repair into thousands, the front arch isn’t as bad, I have a few panels but looking at it it could be repairable without complete replacement
I reckon if you can’t do the work yourself and need someone to do the welding (you and me both on that one!), a sizeable chunk of the battle is finding that person and getting them to fix a time to do it! If you’ve got a good bloke to agree, and he’s said December.... get it done! Gaffer tape is good for taping down lighting cables, but.....! Did you not get dripped on when you slept?! I had a leaky old aerial stub on the cab roof of Clem, and when I eventually found someone to sort it out, he just welded in a patch. The hole was about 50p size, don’t know how that compares to what lurks under your gaffer tape? Apart from my dodgy Halfords rattle can paint on top, you’d never know it was there.
Dynax is a rust treatment, I reckon it's better than Waxoyl, time will tell on the bug. Good for you, these things are meant to be used. Me, I'm just hoping for a short winter and a nice long summer.
Some good work going in there David, my rear roof corner was the same , just repairing the gutter and roof above the tail gate.