Thanks everyone

Words of encouragement always appreciated.
Bantum I haven't used cavity wax but I've used plenty of fish oil inside all the cavities I could get to sprayed with an engine cleaning gun+compressor. It's a good sign when you spray the oil in one end of a long cavity and days later see it seeping through all the seams and joins at the opposite end

Also where I can I'm sealing the backside of welds/repairs with seam sealer.
And Paul sikaflex could work too on bolt holes like that, I can't see me taking the fenders off any time soon once it's finished.
No pics but the past 2 days I've been cleaning up the front/radiator support section to be re-sprayed. The original paint is very thin here and it turns out almost the entire section had surface rust uner the paint. So out with the paint stripper and then I used a wire wheel in the drill to clean up the surface rust. It's the same story on the "crush sections" under the fenders, a single layer of factory primer didn't protect the steel very well, all surface rust underneath

No matter I'm planning on etch priming this entire section myself.
Also starting to clean the underside/wheel wells of 30 years of road grime and mud. Somebody at work put me onto this de-greaser called CT-14 (available at supercrap) and can I just say this stuff is absolute magic! Dilute 10-1 with water for strongest concentration, knock the worst of the crap off with a wire brush and spray this stuff on. Leave it for 15 minutes and hose it off and it looks like new underneath!

I never even knew the original stone chip stuff was supposed to be light grey, always thought it was black

The front wells have cleaned up a treat and I'm onto the rear wells, and the rest of the underside. I will have to take some before and after shots just to show how great this stuff is. Also cleans up suspension parts to look brand new, amazing stuff.