I cant check the facts in the first statement as no link to the data is provided, however I would strongly suspect this includes all the Combined Storm Overflows, (CSO's), which are permitted to discharge in times of heavy rainfall, and as I said, the output would be heavily diluted with rainwater, along with the run off from roads, roofs and other paved areas.
The first link to the Southern Water incidents were between 2010 and 2015. Second was more recent but that was down to pump failure, normally the telematics should monitor and raise an alarm if something goes wrong, clearly on this occasion it didn't. I would also be very interested to hear how you think taking Water back into Public Ownership would solve the issue?
We cant get the NHS, Education, Motorways, Roads, Railways, and most State Operated Infrastructure right, so what makes water any different? All we'll get is calls for water bills and taxation to rise to cover the cost of the investment claimed to be needed to sort things out, and given we seem to be struggling to operate a 'Smart' Motorway properly, then we've no hope with the amount of sewers, pumps and associated assets that would need to be monitored 24/7.
We are still using Infrastructure built by the Victorians, mainly because so much of it was over engineered in the first place, it's still adequate for todays needs. The issue is, and will remain, we haven't got the capacity to collect, store and treat every drop of water that falls from the Sky and makes its way into the Drainage system, and as I pointed out previously, the task of retrofitting separate systems of drainage would be ridiculously expensive, would cause untold disruption, and then we'd have the issue with the existing sewers choking up as they wouldn't be getting the regular flushing through they were designed to have and ultimately need, during times of rainfall.
Which ultimately may start causing more spillages, the very thing you are vociferously complaining about now!
There is no easy solution.