Is true.
Although not doing the tests doesn't necessarily mean the water is less pure - it just means the bottled water industry is less regulated.
UK tap drinking water is about the safest, cleanest and most monitored in the world. The industry that has convinced millions that they somehow cooler or safer drinking from a plastic bottle which leaches plasticisers into water that's been shipped thousands of miles from an unregulated source at the cost of CO2 emissions, instead of drinking free water from a tap, is a masterpiece in the dark arts of get rich quick whatever the consequence business.
If people aren't fond of the taste of tap water, just leave it in a jug overnight in the fridge (covered with a cloth) and the chlorine will evaporate. (Which is much of what you do with an expensive Brita jug with or without filters in it!!)