Is that really the case though?

Nationalisation would of course be supported by debt (just like any public investment), so it would only be a matter of comparing the interest rates to the cost of renting. Well most private companies are supported by debt (as they should), so part of the cost is directly paying for the companies' debt. The state will always have lower interest rates (Since the BoE base rate shot up to 5% in the last 2 years you might have to take into account the maturity of different obligations but this would settle as debt gets refinanced), and taking the first company outlined, "Wessex Waters", their financial report show a cost of debt of 5.2% for 22-23, with a debt-to-equity ratio of about 4 if my maths are good.

What this means is that for Wessex Waters, even if we completely ignored profit margin in the form of dividends (5.4% yield), overhead cost of private business (extremely high leadership salaries, bonus, lobbying...etc) and the fact that interest rates are only gonna rise, it would still be profitable in the very short term to nationalise the company.

Don't be mistaken, what's opposing nationalisation and public ownership is and always has been purely ideological (market is more efficient, national debt is somehow a problem), there is absolutely no financial argument against it.

BONUS: Because if I had to skim Wessex Waters strategic report, might aswell chop up some of the Chairman's foreword:

The high quality of our customer service was again recognised, [...] however, we were extremely disappointed that we failed to maintain our record on environmental performance.

Our financial health has always been, and remains, robust.

I thank the Lord Jesus for his constant grace and guidance and pray that we will be able to rise to the challenges we face.