The rust in the pic was just light surface stuff, I gave it a good scrape and a wire brushing and soaked it with ku-rust. It willl be properly cleaned up & sealed before the new wing goes on. The wing had no arch liner by the way which I guess is why the water got this high up. Caught it just in time really.
This is our other gti, it had an arch liner so the same place as the red one is pretty clean, the wing was a replacement, however, it was painted but not sealed on the back or where it bolted to the car, when unbolted it just fell off!

