If you fit a 500 or 1000 litre tank to catch the rain that falls on the roof of your house, you can beat the hosepipe ban, reduce your water bill and have a ready source of water for the garden.
A properly constructed tank of this size needs to have a filter over the input pipe and to be completely light-resistant.
If your garden is level with the house or lower, you can connect the output of the tank to a pipe laid in the soil and leading to to an outside tap. (Note that the pressure at the tap will not be as great as from a mains tap.)