SACK THE BLOODY ROBOT PAINTER LAZY SODThe inner wing has very little paint and no under seal let alone rust protection , if the plastic wheel arches are missing there is nothing stopping the crap and then corrosion forming.
The best solution is to remove the outer wing and drop the suspension down , clean all the rust off , treat rust killer then with a zinc inhibitor, then hammerite , then a decent underseal.
I had no signs of rust but recently did mine as a precaution although i didnt drop the suspension i sprayed a rust inhibitor all around there and then brushed underseal on top.
This is the amount of paint under the arch!!!
There is also only a thin coat of paint on the inside of the outer wings
These cars are timebombs for corrosion
Its unlikely to rust from the engine bay down as the paint in the engine bay is good and its shrouded from the weather, underneath is a magnet for dirt and moisturewttc mate, i have same problem on car im buying im just going to hammerite over it as it looks like its just a bit of rust in the bay!