UK engine / suspension and other bits would come from places like Real Steel (Middlesex), US Automotive, John Woolfe Racing. TopSpeed and a couple of others i can't think of.
The rust spots from the outside are the rear window bottom (collects water easily).
Look at where the door handle is, then go all the way down to the bottom of the door - the panel on the left is the front part of the quarter panel. That is a very common rust spot. Check for any signed of non straight metal that would suggest previous work that could be rusting, or just general signs of rust / bubbling. The best way to check is by taking out the vent in the door jamb (1 bolt) and getting a torch in and seeing the visual state of it. Maybe even taking a phone pic with flash enabled will work. Now, run along the bottom of the door, so you're on the floor and looking up, as the door bottoms are a common rust spot. Move all the way to the front, just as you get to the front tyre you'll be under the rear part of the front fender. It tucks all the way under the body and that is another common rust spot, check around the bolts to see the state.
Then, get under the car to see the chasis legs. The front is usually ok and it's pretty heavy gauge steel. The rear chasis legs, especially around the top near the fuel tank where the suspension mounts to, can often corrode badly.
Hope that helps!
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