NR already have a nice report from 3.5 years ago on why delays had increased in the preceding years (and newer material too for certain routes too). There are direct causes and indirect impacts that multiply them. The biggest direct delay increase cause within railway control are station dwell times being unrealistic, passenger usage has increase but the stock can't cope (e.g. trains not full length, narrow doors, not designed for standing) so that real dwell times were longer than timetabled dwell times ideally needing action in both directions: action to reduce dwell times and being realistic about timetabling.
The May 2018 southern timetable showed the benefits of being realistic on dwell times. (the southern network has the largest indirect delay multiplier due to network geography and lack of grade separation)
The new SW and SE franchises are mandating action on the rolling stock side.
Abellio Anglia seen resistant to accepting realistic dwell times in the future as then they wouldn't have enough rolling stock for another reason it also enables more blame to be pushed on NR.
One thing from the old NR report that has hardly seen any action is the importance of spreading people evenly along the train - this often means improving canopies so everyone does try to use a small number of doors at a station when it rains.
station dwell times can be compensated by better acceleration of rolling stock procured, or elimination of "tight spots" in the route which require hard deceleration to a set of obstacles,and then hard acceleration back to line speed on the other side.
on a rural route for instance, you can quite easily shave 2 or 3 minutes by a less severe grading of one set of points from a 20mph crossing to a 35/40mph crossing.lots and lots of those on the network,but they've been neglected for decades.
as for hydrogen trains, it's another fad.LNG will be much more useful.
Hydrogen has a very low calorific value,and needs insanely high pressure systems to work effectively.From a health+safety point of view it's batsh*t crazy!
(ok so hydrogen tanks get stored on the train roof so the gas cloud goes up...problem is it also goes out radially a LOT faster than a better controlled substance,hence more explosive.in the case of operating under the wires, given a decent amount of humidity/environmental conditions you have a very ready source of ignition)
LNG we are fortunate to have in spades in this country, far cheaper than diesel and rather less troublesome when you have problems.
the technology everyone
REALLY wants to have is the enzymes that can convert plastics and long chain esters/hydrocarbons/polymers like carrier bags and Coke bottles , back into useable short chain types like propane/butane/hexane//heptane/octane