Led by whom ?
They're all pretty much shot - they're suffering from various corrosion issues, the wiring is knackered, spare parts are getting harder to obtain and they need silly amounts of maintenance that the modern railway can't provide.
New designs can do twice the mileage with half the maintenance hours, that's also the underlying reason for SWT Class 455 AC motor conversion, for Class 321 AC motor conversion and helps the costs for Pacer withdrawal.
Depot space, jacking space, they're all at a premium, if a unit can be lifted less often, lifted in half the time, and needs little more than exams when it's on depot, if repairs can be completed in half or a third of the time, keeping old stock becomes a problem, particularly if you can then run more diagrams with fewer units, so you don't even need as many man-hours to do exams.
The industry is changing, it's not about the number of trains in service, it's about the number of seats you can provide on a route now, and sometimes throwing more stock at a route isn't any sort of solution at all.
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Who wouldn't want a badly built, incorrectly wired unit ?