Isn't one analogy the withdrawal of the HAPs off the South Western division in the early 1990s without replacement, which you have described in the past? Eventually by the end of the decade the ridership came back and SWT had to bolster their fleet with CEPs off the South Eastern side.
Yes that's a good point actually. Don't think it was quite as severe as the loss of the 455s and 313s (as there were perhaps only 15 or so HAP units left on the SWD by this time) so it led to shortening formations rather than cuts. The cuts (mostly to peak services, to be fair - the off-peak offering remained quite acceptable) occurred in May 1991 with the HAPs still around (they went in Sep 1991), presumably as a reaction to the recession. That said, there were savage if temporary off-peak cuts to the Portsmouth Direct in May 1993 with just 2tph, even north of Haslemere.
Improvements happened then quite early on in SWT days, the 1997 timetable was a pretty high-frequency one, and that was before any CEPs arrived. By 1999 they had: this partly enabled the high-frequency timetable to come in, presumably, but also ISTR more 8-car off-peaks were diagrammed compared to most of the 90s when it was largely a 4-car off-peak railway (or 5-car on 442 routes).