Best option is to aim for a smaller population, estimate optimum population for the UK is about 20 million.

They dont need to find extra billions of litres, the need to stop losing billion of litres, due to leaks from an antiquated system that suffers from a lack of investment in updating the transmission infrastructure. This is mainly due to excess profits being pocketed, instead of being reinvested.

It's well past time that we stopped using treated mains water to flush our loos (in the uK about 1/3 of total water use/person). It's completely insane. Planning permison for all developments (both domestic and commercial) should include a requirement to provide adequate storage of rainwater for toilet flushing. Problem solved. It would also mean keeping toilets clean would be a lot easier in areas with hard mains water and hugely reduce the need for agressive chemical cleaners.

Not very likely at all. The island is surrounded by water for goodness sake, and there are various low cost technologies already developed to provide desalinated water. How about the single atom thick membrane that takes all the salt out of seawater for instance, whatever happened to that? Read 'Scientists Have Invented a Graphene-Based Sieve That Turns Seawater Into Drinking Water'. https://www.sciencealert.com/scientists-create-a-graphene-based-sieve-that-turns-seawater-into-drinking-water

Worzel, I could not agree more. Fat cats make money, whilst business -no pun intended- goes down the drain. The worst thing for this countries infrastructure was selling it off to the private (money grabbing) sector.
martinwinlow, again, I agree with your comments. It is ludicrous that all that available 'clean' water is wasted.
Eric Blenhiem, this is Britain. They do not do things that are good for the country until it is too late and costs more to do at that point, and of course, in the meantime, the people suffer from the Governments incompetance.
Just look at the flooding the UK has suffered this year already. The total misery of those affected is heartbreaking. Why has someone not invented a simple way for people to protect their homes? Something that home owners can fit to their home to stop the water getting in. Sandbags are pretty useless as you would never have enough of them with some levels of flooding.
Sorry, off topic. That floodwater can be saved in emergency reservoirs. Better still, get some more made up and then take the others off line/divert the water whilst the ancient infrastructure gets fixed/updated.

Many desert communities used to use prepaid water as a sales incentive. Green lawns and trees and evaporative cooling were promoted as value added features.

There are several ways of desalinating water, using electricity, which can be generated by using renewable methods. The usual argument is that renewable energy is not base load energy, we have heard it before, if the wind does not blow, no generation, if the sun does not shine, no generation, but the point that is often forgotten is that to use renewable energies for desalination, it does not matter if it is base load energy, intermittent generation is quite OK. There are plenty of wind turbines in the UK, and that energy that is not put into the grid or storage could be used to proved clean drinking water, or for normal usage. It should be remembered that if the mains and drains are not flushed regularly, the sewage system will be blocked and not work.

If folks are worried about inconsistency in the power generation to operate desalination plants, why not take advantage of a handful of factors present in abundance? Wave power in the North Sea is constant pretty much, the deeper water there is quite cold which could lend itself to thermal difference power generation, and tidal power generation is quite predictable as well. Wind turbines and solar might be more mature technologies, but they're far from the only ones. And this coming from a guy who works in the O&G service industry.

1) Deport bad actors. With fewer people, the water needs are lower. 2) Fix all leaks in the existing pipelines. 3) Ensure that people are conscious of their water use. People from other cultures can be unaware of the need to save. 4) If needed later, add desalination plants and catch more rainwater.

Of course, in Britain, what will happen, is, that when the system breaks down, and there are serious water shortages, the privatised companies will plead poverty, and ask for government/tax payers money to fix the system, but will continue to pocket profits in the form of share dividends.