I worked for 2 State Owned industries: BNFL and later CEGB
BNFL contracts with CEGB were:
Return on Capital Employed (ROCE) during construction and Capital Write Down and Cost Plus during operation and decommissioning.
ie BNFL were incentivised to maximise costs at all stages: The more they spent the more "profit" they made.
AT CEGB the trump card was the "Obligation to Supply" - a statutory duty to provide Generation capacity. Many projects Nuclear and Non Nuclear were justified on this basis with very limited challenge.
CEGB had 14 Regions and 14 Nuclear Power stations: One in each semi-autonomous region, the first stage management of the 14 Stations came together was one layer below the main CEGB Board.
Each Magnox station was designed and built by a different Consortium with Patented fuel design details, requiring Jig Changes to strip off the Magnox casing in the B30 fuel plant for each fuel type. In itself that was a costly exercise - but was the root cause of many of the difficulties faced in reprocessing in the 70's/80's.
France decided on a PWR design and built them like a Production Line
My wife worked for British gas, she has similar tales of organizational inefficiency. eg13 semi-autonomous regions with duplication of management and operational level functions
You'll find no shortage of inefficiencies in the private sector. The last company I worked for had expensive research duplicated by different groups
in the same building, because they don't talk to one another - and that's thanks to management. There is an assumption that appears in these sort of debates that the private sector is more efficient than the public sector. That's not borne out in reality. There is more scrutiny of the public sector, so expensive mistakes are more likely to be publicised. You've doubtless heard of expensive failures in IT projects in the public sector - but not similar failures in publically listed companies: for instance I know of one major supermarket which spent an eight figure sum on an IT project that failed to produce any meaningful results.
You mention that the CEGB had an "Obligation to supply" requirement. This policy resulted in the UK having one of the most reliable electricity supply systems in the world, with a very comfortable reserve of capacity from multiple energy sources. If we'd still had that, we would not be so dependent on one fuel source - gas - and so wouldn't be in such a mess now.
One last thing: it's expensive building power stations. Hence the so called "dash for gas" in the 90s, as they were cheaper and so produced a swifter return on investment. One consequence of that is that we no longer have the
reserve generating capacity that existed during the CEGB times: that's not profitable! But, well, we've lost 2 GW in nuclear and 2 GW in coal this year and even before this crisis things were looking very tight. But now forward electricity prices i n France are almost twice that in the UK - that means the market will be using the 3 GW of interconnectors with France to export power from the UK. (Indeed, energy flows have been almost exclusively from UK to France even over this summer, which is simply unprecedented.) We were depending on being able to import energy from other countries - but that's looking doubtful. It is likely to be flowing the other way, from us to France as a result of market pricing. Power shortages seem inevitable, especially during times of little wind. Industrial consumers will probably be cut off during peak hours. Rolling blackouts are also a possibility.
Think about that for a minute: while energy traders will make a killing, it will cost UK industry - and us - many more billions in lost productivity. That doesn't seem to be a very good benefit of liberalisation in the energy markets, does it? Best to hope for a mild, wet and above all windy winter. Oh, and stock up on candles...