For years we were told that the introduction of the IETS, and the new EMUs for the Thames valley services would greatly reduce overcrowding, not only on the routes thus served, but also by freeing up cascaded stock for use elsewhere.

Not much seems to have happened.

Which service is that ? So much for the assurances that all busy services would be full length. I appreciate that things are slowly getting better, but we have had well over a year of routine short formations.

Work on the new nuclear power plant has now stopped.
Details from news media of your choice.
Some reports refer to "work being suspended" whilst others call it "cancellation"

Hopefully the well understood increase in pressure at high temperatures has been thought of.
And of course even if the train is not actually moving, but is available for service, then some hydrogen will be consumed for auxiliary purposes. Any consumption drops the pressure in the tank.

I fear not, only suitable for branch line services.

Numerous remarks were made, all critical of short formations, cancellations, no reservations, not enough toilets, and no buffet.
these remarks included;

"trains that don't work"
"half length trains"
"new shorter trains"
And many other slightly differing ways of expressing dissatisfaction about the new Hitachi trains, and consequent doubts about the wisdom of purchasing nuclear reactors from the same vendor.

Two local political figures whom I met at a social event are very critical of the IETs, in particular the absence of buffets and the number of short formations.

These politicians are not in my view well informed on railway matters, they simply observe that the new trains are "often shorter than the old ones" and "never have a buffet" and often "not even a trolley"
Both have experienced repeated standing room only trips on the new shorter trains.
Both have had many letters from local voters demanding action about the trains.

So far as I know, neither of these politicians have any direct influence regarding the proposed nuclear power plant. However both expressed the view that the new trains are a failure and that if "Hitachi cant run full length trains, who wants to trust them with a nuke"

Indeed, there is more to Hitachi than IETs and a nuclear power plant at Wylfa.
However two failures tend to be much better remembered than a dozen successes.

According to various reports, the proposed/promised/planned new Hitachi nuclear power station at Wylfa is likely to be cancelled due to concerns about escalating costs and growing delays.

Whilst this appears of little relevance to the IET problems, it has been suggested that if "Hitachi cant even build a train that works, whom would trust them with a nuke ?"

Is the Hitachi brand becoming toxic?

I doubt that detailed and accurate records are available from the Brunel era, but it is known that many lives were lost in the building of box tunnel, and on other large civil engineering projects.

Common causes of death included being crushed or buried by cave-ins and collapses, falls from a height, run over by wagons, and accidents with explosives (gun powder in those days, modern explosives are safer to handle)

Modern health and safety standards add to costs and to the time taken, but OTOH modern machinery increases work rates, and powered machinery reduces the numbers of workers engaged on a task, and therefore also reduces the number of potential victims if an accident occurs.
Medical care has improved greatly, many workers today survive accidents that would have been fatal in earlier times.

Present day safety standards should NOT be blamed for the Crossrail delays, these standards were known about at the planning stage and should have allowed for.

Perhaps several could be coupled together and equipped with a small engine, pacer replacement ?

Presumably the "Autumn 2020" opening is now in doubt ?

Back in the good old days, such lamps would have been duplicated, one oil lamp in case of power failure, and one electric light in case the someone forgot to fill the oil lamp.

Changeover controls are indeed themselves a potential point of failure, and should IMHO be avoided when possible for lighting.

A better approach for large stations is to connect roughly alternate lamps to different supplies, without any changeover panel. Failure of either supply would still leave half the lights lit.

If changeover controls are needed, these should be duplicated with each set supplying half the lamps.

For example "odd numbered lamps" are normally supplied from substation #1 but change over to substation #2, if #1 fails
"even numbered lamps" are normally supplied from substation #3 but changeover to substation #4, if #3 fails. These two sets of changeover switchgear should be in different locations, to protect against fire or other accident affecting both.

Failure of any one supply leaves 100% lighting. Failure of either set of changeover switchgear leaves 50% lighting.

If BOTH sets of lights go out, for example due to a large scale external power cut, then a third set of lamps that are normally unlit should come into operation.
These would be of much reduced power, about 2% of normal lighting levels will suffice in an emergency, possibly less.
A rule of thumb for emergency lighting in large open plan areas is about one tenth of a watt per square meter.
That relatively modest loading may be obtained from a generator.

Media reports state complete failure of station lighting last night.
The only illumination was from the lighting in the many retail units.

Does not look like a general failure of the public electricity supply since said retail units still had power.

Have network rail not heard of standby generators ? Or a secondary electricity supply derived from the traction current? or even of dividing station lighting between two different supplies on different substations ?

https://www.bbc.co.uk/news/uk-46804914