I took that line in the ad with a truck load of salt don't worry. I was expecting rust for the price! I added the picture of the ad in for comedy, not because I'm bitter.
In fairness though, there was no visible rust at all aside from one bit on the rear valance. The rest was only visible either with the sill covers off, the arch liners out, the boot trims out, or the interior carpet out. Or other sound proofing/covers/etc. Or in the wheel arches, the wheels were in the way, or the rust was covered up with the factory stonechip paint and I didn't happen to poke it in the precise area etc etc...
It was an old boy I bought it from, who drove it daily, and always let a garage "look after" it, and I have no doubt at all that he genuinely believed there was indeed "minimal rust anywhere".
I probably should have asked if I could remove various panels and trims etc but lets be honest, would you let someone start taking your car apart if you were trying to sell it?
If I were otherwise inclined I could easily have doubled my money by breaking it for parts, such is the value of E30 bits these days, but by the time I actually went hunting for rot, I had taken it around all the shows and grown to love it, so I couldn't do that.