Almost all I would say, workers, customers, stakeholders. The infrastructure that was included within the privatisations was steadily run down as the assets were sweated in order to maximise shareholder returns. Historical good egineerng practices were often dropped with is very demotivatng for skilled employees. Investment decisions were solely based on return on capital employed rather than historically based on the assets and infrastructure the country needed, this was partially important when trying to develop changes in technology which private firms see as much riskier. As a result the UK which was seen as a global leader in energy, in the days of the CEGB, has become nothing more than a series of foreign owned outpost subsidiaries. This explains why the UK develops and manufactures very little energy technology and is increasingly influenced by geopolitics (for example big changes in the German market have impacted negatively in the UK as E.ON and RWE withdraw investment and EDF with is 85% owned by the French Goverment has to please French ministers).
One biggest impact is the grid system which sits with almost no extra capacity. Now while sucessve governments carry a big chunk of the blame for this the unwillingness for energy firms to invest is equally as important. Additionally the distribution networks consistently change hands between foreign investors seeking stead rates of return which is very hard to achieve without impacting on infrastructure investment.
All the talk at the current time from Amber Rudd is low cost energy. consumers have seen year on year price increases and market exploitation by the big six ever since privatisation. With coal, oil and gas at record lows our energy bills continue to sit at very high levels.
There was huge waste within the nationalised industry, but it's easy to see the same waste in the current industry. It would make in interesting study to compare the total overhead in the 1980s to today (in real terms) I would wager its far greater now.
I was a fan of privatisation when it happened but now believe it has mostly been negative for the stakeholders and customers.