I all honesty, I don't think you can use a hosepipe even to fill a bucket... the missus works for the local Water Board..... so will double check..
However, I know you can use a hosepipe for ;
Washing a commercial vehicle (but has to be labled as such)
Filling a fish pond, as long as there is fish already in it...
Washing down a driveway
Filling a paddling pool !!
Luckily, I can use the hosepipe for the car... just take it 3 miles down the road to work, and I'm in a different water area that doesn't have a ban....