i wouldnt even dream of using a carwash or asda's/b&q's resident scratch terrorists,its against my religon.
I saw one of "them" washing a really dirty range rover. I sh#t you not, I saw him wash the really muddy, gravelly wheels 
first, and then move on to the wing above the wheel with the 
same sponge, 
without rinsing it. 
   
   
I was hopping around all over the car park pointing it out to my missus (who thinks I'm a bit weird with car washing procedures), going "LOOK, SEE, SEE, TOLD YOU SO!!!!"