I wonder if the diagrams are not being met due to problems handling the 10car units - 8car depot/siding space in the required location(s) won't work.
Perhaps pairs of 5car 701s are needed for all the current planned diagrams to work ?.
(goodness knows how much joining and splitting SWR is heading for pre morning peak and post evening peak).
The units not in service from past allocations are either at Wimbledon or Clapham. None look to have broken in service or been out of service for more than a week. A continued maintenance backlog perhaps, with the false dawn for 701029 the other units would be worked harder and come up to exams quicker with less spare units to be on maintenance.
Some units have sat at Clapham for a bit which seems unusual. Could some be used for other purposes on rotation in which case the target is more challenging than it looks.
5 cars wouldn't really help 10 car maintenance, Wimbledon would see the units less frequently as more paths would be taken up by 5 car units (even with some additional ones at 5-car, though not sure it's necessary in the current weekday timetable). What it would allow is a lower availability target in current timetable, only needing 84% of vehicles in traffic each weekday rather than 88% now.
I also think the fitter learning curve might still be being climbed.
Very tempting to think that getting shot of the 458/4s would simplify things. But then do these need to be kept warm and healthy until hand-back (due next year ?).
Reliability is still a focus for the 701s, as much improving the units than just the people getting more used to them. Longer term SWR have recently put out a tender for the next design phase of Wimbledon depot enhancements, that will take years to see any benefits if it happens.
The performance strategy published earlier this year quoted 51 diagrams to avoid reliance on the 458/4s, either 450 availability is slightly worse or more have been shifted onto longer distance work than the plan assumed.
I still marvel at how 25 x 5car 701/5s can be accommodated without having to be used !.
Theoretically there was a plan for all 30 x 5cars and the 458/4s SWR currently have to be in active service. How painful that plan would have been is a separate question. Strawberry Hill taking some of the 458/4s will free up more space and the few 701s not on SWR metals will also help.
