Due to unconstrained urban construction (which does not pay for water infrastructure), and global warming, the water system is badly overloaded at times. Population has increased by 10 million in two decades. Something like £150bn has been spent updating the system (about £6k per house), but it is not enough. Probably the same again is required, so it comes down to over what period do want to pay for it in your bills - 5 years? 10 years? The system was in a terrible state when it was privatised after 50+ years of neglect, so unless you are sure future governments will behave better I would suggest leaving things as they are. Personally I am OK with doubling my water bill to more realistic levels, but I suspect many won’t be.
This country has a very serious shortage of engineering and construction skills, so the shopping list of people’s projects needs to be rationalised. Power stations, rebuilding millions of homes, windmills, hospitals, new national grid, water, roads etc etc. The work can’t be liquidated without big increases in wages and cost and huge numbers of highly skilled expats from abroad. I don’t think this country is rich enough to afford it all over such a short timeframe.