Yes, we've had this discussion before about stock availability for events and that rail companies can't afford to have spare stock in sidings so have to rob Peter to pay Paul when an event is on. Glastonbury next.
and
[Broken record mode]
Of course if they were to electrify all the GW▸ main lines (including Swindon-Gloucester-Cheltenham), all those Electrostars that either sit at Reading or move air in 8 or 12 car formations that used to be 2, 3 or 6 car Turbo services on the Thames valley routes could have a day at the races to help........
I strongly suspect the latter is even more unaffordable than the former....