I'm inclined to agree that privatisation is bad for long term planning, but the history of the Abingdon Reservoir proposal seems to be counter evidence:
Looks like Thames Water (a private company) proposed the development nearly 20 years ago, but it was turned down by the Environment Agency, a government body.
> Plans for a £1bn reservoir in Oxfordshire to supply more than eight million people over the next 25 years have been rejected by the government.
> Thames Water wants to build a site on four square miles of land near Abingdon to help ensure future demand is met.
> The bid went to a public inquiry but the secretary of state said there was "no immediate need" for such a site.
"Abingdon £1bn reservoir plan rejected by government"
https://en.wikipedia.org/wiki/Abingdon_Reservoir
Looks like Thames Water (a private company) proposed the development nearly 20 years ago, but it was turned down by the Environment Agency, a government body.
> Plans for a £1bn reservoir in Oxfordshire to supply more than eight million people over the next 25 years have been rejected by the government.
> Thames Water wants to build a site on four square miles of land near Abingdon to help ensure future demand is met.
> The bid went to a public inquiry but the secretary of state said there was "no immediate need" for such a site.
"Abingdon £1bn reservoir plan rejected by government"
https://www.bbc.co.uk/news/uk-england-oxfordshire-12651131