well I have some photos illustrating the horrors of tinworm, is there an easy way of posting these
onto the forum as an illustration of 'what could be lurking behind'

without breaking the bytes bank. (I think there are 17 photos)
One interesting point, as can be seen on the floor in one of these photos an awful lot of muck can find its way into the gap between the two skins. I couldn't imagine how but apparently the top radius of the wheel arch liner (rear) did not quite meet the return lip of the wheel arch (and I am advised probably never did) and muck/moisture found its way through this gap.
Worth checking as it would appear to be another weakness in manufacture. The build up of moisture is released by a small drain hole in the underside of cill, (and this is easily blocked with an underseal application), but the damp muck settles and eats away. This is not evident on the photos but can be easily inspected on the car with a mirror after cleaning out with a brush.
The bodyshop did not taken any photos of the finished article, but it is now as new in this area on both sides. (can provide these if anybody wishes to see)