2009 corrosion issues , no warranty !!!

Hi Im speaking on behalf of a friend who has a problem with his land rover and i belive land rover themselves are trying to fob him off with unreasonable excuses .
The problem has started with some corrosion on both sides of the vehicle just infront of the rear wheelarch on the flat of the panels , It feels like the corrosion is right through the panel as you can feel it on the back and see it on the front blistering through the paint , Whats quite strange about it is there is nothing behind the back of this panel which may have pointed to the problem .
My friend has taken it back to the dealer and they have spoken to the warranty office at Land Rover , the response that came back was unbelievable , Land Rover have said "its because the vehicle has been used in arduous conditions and has not been washed correctly in accordance with there guidance" ????
I can honestly say that this guy has the best kept land rover i have ever seen , he lives in the middle of town and uses it for taking his spaniels up to a field to walk and thats it , Its covered 29k miles since it was new in 2009 .
Can someone offer some advice .
Best Regards
Graham

Involve Trading Standards.

I know LR had issues with the paintshop, grit under the paint on Discos I think. The car is only 2 years old, it's not unreasonable for it not to corrode within this time.