When we stayed at the Heathrow Windsor Marriott in June, we managed to scrounge some water from reception (given we'd just flown in on transatlantic flight) as they are withdrawing water bottles to cut down on waste. In the lounge they don't have bottles of water, instead they have what looked like a beer tap that filled (your own) bottle with either still or sparking water. That perhaps might be an explanation for other properties following suit?