How difficult can it be?
COllect water in a water but or bucket for the garden, use left over dishwashing water, or even water from the bath for watering the garden.
Bathwater or a bucket of water for the car.
Yes, it's a bit more hassle, but there is a hosepipe ban. In april. For a reason.
I think those people who are saying 'well, I don't see why I shouldn't use it' are no better than people who chuck rubbish out of their cars because they don't see why they should take it home with them.
GRRR