I worked a lot on classic Mini's, Metros and Maxi's. The degree to which body work had been patched and bent to match it to the corresponding chassis was quite amazing. Rumor had it the Leyland factory had a guy with a very large hammer standing at the end of the line to 'adjust' the doors if they didn't close properly. I totally believe it. I've seen almost new subframes that were Swiss cheese from rust and/or with very bad welding.
That said, there are few cars that are more fun to drive than a souped up Classic Mini, and even fewer that would be as lethal in an accident.