Old frame collected, loads of build/help questions

I've just picked up my 531 Professional Hannington frame set, for £100 it was a bit of a lottery.
I think it's okay but I'd love some help.

First it has rust in just one area that I can't rub down to shiny steel, is this a major issue?

The forks have alloy oval plugs in the crown, I've never seen this before and one is missing. Any help here would be great. I suppose a bit like the 'coins' in Gios frames.

The farmer who found this also gave me some wheels as freebies as they weren't in the sale. The rear is a stunning Mavic Argent sprint on a nice Cyclone hub with a 5 speed straight through freewheel.
The front is a LF Normandy with no internals, what would fit?

Bonus bits are a set of early nutted 105 calipers and non aero levers with mint hoods.

The sad bit is the Campag chainset looks like a Strada? but is very very badly corroded and has Williams and Zeus ring, the BB is fine as are the tapers. that's going

Here's the odd 'missing?' cap


Fixed the Normandy with an old Mailard from a gas pipe Peugeot.

I don't think that cap has any structural function, it's just there to keep the weather out..Shouldn't be too much trouble to shape a bit of alloy to fit in there and epoxy it or something. Take a rubbing and use it as a template?
Where is the rust on the frame?
Pic. of chainset would help identify it... It's probably salvageable with a lot of work. Hopefully tapers and pedal threads are sound.