the factory placed that paint on so long ago, why would some one need to take it off? it has been primed and sealed by professionals so long ago, and is doing a good job, even to this day. you're destroying a 30/40 year bond. why would you need to see whats between it? surely if its still there it must be good to lay a coat of paint on top, you already have a perfect base to lay your new coat on top. You only need to bear metal the 'rusty bits'. You're removing all that lovely red oxide paint applied by morris.
As to the little bits that are lurking under the paint, well that paint is not attached to the metel, so a little sand and that paint will come off very easily. The surface rust detaches the paint from the body. The rust you found was probalby caused by someone else bare metaling in the past.
As for 2 pac. it was never on a morris so why are you putting it on, its a quick cheap fix, that's why it was developed, by the car industry to get a good shiny finish without any effort. and it is causing many problems to the purists when they want their car restored to original. celli will never be discontinued in the near future, there are too many classic cars around the world that need it, (the good ones). 2 pac classics just dont look right. (looks great on my Ducati though).
Funny how 2 pac turned out to be more danergouros to your health and the enviroment. so now it is going to be stopped. I think there is a new water based 2 pac being used now. (i dont use 2 pac so i dont know).
the fact is once steel is exposed to oxygen it oxidises so the rust has started.
ps. so dont get a bucket of water to wash your paint stripper off!
Kirstmin, this bare metaling is the reason why you have such thin paint.