I have just been to Halfrauds and seen a new product by triplewax. It is a car wash solution that does not require any water, hoses etc.
Quickly reading the back it explained that you first remove loose grit from the lower areas of the car, then apply the magic formula panel at a time working your way down which lifts the dirt, then simply polish off. They also claim that this will NOT scratch paint.
Who's gonna be first to try this then?
I too live in a hosepipe ban area (banned since last June) and have got round this problem by converting an old Wormery into a water butt and use the gravity feed from this to a hospipe to my pressure washer which sucks it through.
HTH
Rich