@Justthefacts
You neglected to mention a key reason UK trains "run on overtime". The employers make the choice not to have plenty of train drivers, so there is almost no "slack" in the system due to that deliberate understaffing policy, a driver or 2 calling in ill and its a desperate search for someone to do some OT (or, as is sometimes the case, schedules get shafted by a cancellation or two instead).
I know a few people who work in the rail industry, including drivers, one of the drivers is a female and gets really irritated by the frequent requests to do OT (as she prefers just to do her contracted hours so she can see more of her family as base pay is decent especially for this area of UK & family time worth more to her than OT), occasionally she succumbs to pressure to do OT (& mainly because she knows what OT her colleagues have already committed to & so feels the need to do some just so they get a bit of a break from the cab). It's a high pressure job * so deserves good pay, peoples lives in your hands, need to be vigilant - plenty of situations where objects thrown on the line, or fall there ** (not to mention nasties like reckless drivers failing to beat barriers & vehicle getting stuck in a crossing, through to the trauma of the suicide by train minority - a depressingly large number of people choose that method & it can be very traumatic for drivers who have that happen to them)
There's a misplaced superiority complex view of many in the UK that makes them very upset that a train driver gets well paid, instead of celebrating the fact they are providing a useful service (more useful if train companies were not allowed to charge such extortionate fares) and doing a job where peoples lives are in their hands
* in addition to being responsible for passenger lives, there's lots of training involved as its not as simple as just following the tracks, plenty of UK lines are not straight for long and safe speed on certain sections of line can be surprisingly slow (drivers have to "learn" a route and its quirks*** before they are allowed to drive them ), plus regular health checks, regular very strict drink / drug tests (which could deter many candidates due to effects on social life). There's also issue that different types of train need a different set of training (different layout, different performance, braking, / handling etc.)
** trees / branches on line quite rare as most train companies have an over aggressive approach to vegetation and instead of regular trackside maintenance crews they just clear fell trees for a huge distance either side of the tracks (generally until they reach boundaries of land they own)
*** a lot to learn as anyone who has seen complex rail points systems and areas of multiple tracks e.g. near stations will know