The UK currently doesn't do even the most trivial of reuse. But the privatised water companies would rather impose metering followed by price increases to deter consumption, since that'll mean more money for them.
Water reuse is a great idea. Although it's worth pointing out that the UK looses 20% of it's water to leakage before it reaches anyone[0]. Private water companies taking a basic amount of responsibility for maintaining their assets would do a lot before even talking about water reuse, rain harvesting etc.